This question comes from a slightly related one.

At the time of WW2, most US industry was on the East Coast, including all of the shipbuilding for Carriers and Battleships. If the Panama Canal went down, it would greatly reduce the logistics of the US Navy in the Pacific.

So I want to know, did the Japanese Navy have the ability to destroy it in a surprise attack, let's say on 1941 Dec 7?

What I know so far:

  • The Panama Canal has 6 water locks per lane. The locks have concrete walls but hollow steel gates, as per this documentary: https://www.youtube.com/watch?v=d-CaBIKTl4M , at 1:11:00 you can see they are a hollow frame. 1 bomb or torpedo will probably blow a hole in it, though it might not be enough to instantly drain the locks.

  • Japanese Dive Bombers had the training, as evidenced by the many carrier hits they got in early WW2 (Coral Sea, Midway.) Note, I'm talking about hits, not necessarily kills. I reviewed those two battles and many times, the US Carriers got hit but survived (US Carriers seem a lot more stalwart than Japanese Carriers at that time). I'm only trying to point out that Japanese Dive Bombers seemed to have good training and accuracy.

  • Edit: The Panama Canal Locks are powered by the Gatun Hydroelectric Dam. Maybe all you need to do is smash that dam, and the locks are suddenly worthless. I do not know for sure how long it takes to repair a hydroelectric dam, but it has to be on the order of months. From reading about bouncing bombs going after dams in Germany, they appear to be significant logistical targets.

  • The Doolittle Raid (made by America) got 2 carriers, 4 cruisers, and 8 destroyers very close to Japan before being detected, and that was when they were already at war (1942 Apr 18).

  • Japan actually designed and built some submarine aircraft carriers meant to raid the Panama Canal, so apparently they believed the Canal's defenses were not good enough to stop an aerial attack.

  • The surprise attack on Pearl Harbor IRL was a total surprise, despite seeing airplanes on radar.

What I don't know:

  • what AA defenses the Canal had at that time.

  • what range and endurance a Japanese Naval Group had.

  • possibly other things that make it impossible or unlikely.

I'm trying to keep this specific so it doesn't get closed as too broad or too opinion based. I'm asking if the Japanese Navy had the ability. I'm not asking if it was a viable strategy or sound war plan.

  • 27
    While there's an obvious point to destroying the US fleet, what would be the tactical or strategic point in destroying the Canal alone? The US had adequate rail transport for goods, munitions, and fuel. Moving ships from the Atlantic to the Pacific by going around South America would take a bit longer, but not that much when you consider construction times. It might have made sense to hit the Canal in addition to Pearl, but I doubt the Japanese had the capability to do both effectively.
    – jamesqf
    Nov 5, 2016 at 18:20
  • 9
    Besides, my understanding is that the Japanese hoped the destruction of the fleet at Pearl would keep the US from entering the war against them. From that point of view, there'd be no point to hitting the Canal as well.
    – jamesqf
    Nov 5, 2016 at 18:22
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    @jamesqf I never said this was an entire warplan involving destroying the Canal alone. I'm just looking at it as an individual target. It's strategic importance is obvious. Going around takes a LOT longer, I believe 1.5 months. There may also be a Northwest Passage above Canada, but only open a few months in summer and probably taking a similar amount of time. Disabling the Canal would temporarily split up the US Fleet and probably force part of the Pacific Fleet to guard the Canal in the future.
    – DrZ214
    Nov 6, 2016 at 3:46
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    But here's my broader point: we could argue all day about how bad (or not) the loss of the Canal would really be, but the OP question is, Does Japan have the ability? I don't wanna get into Canal vs Pearl Harbor, or Canal vs something else either. I tried to specify the scope of this question to, does Japan have the ability to destroy the Canal in a sneak attack before war is declared? Otherwise it'd proly be too broad or too hypothetical.
    – DrZ214
    Nov 6, 2016 at 3:47
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    @user14394 "You can't attack Pearl Harbor without a plan for a follow on attack against the Panama Canal." Buh? The Japanese did exactly that. You can claim that it's a bad idea, but claiming that you "can't do" something that manifestly was done makes no sense. Nov 6, 2016 at 13:17

8 Answers 8


So I want to know, did the Japanese Navy have the ability to destroy it in a surprise attack, let's say on 1941 Dec 7? I'm asking if the Japanese Navy had the ability. I'm not asking if it was a viable strategy or sound war plan.

Well, you're getting both. :) Evaluating it as a war plan is WAY more interesting.

Yes, but...

  • It would be fixed in six months.
  • Shipping can still go around South America.
  • They'd have a hell of a time getting there.
  • They'd have an even worse time getting back.
  • They'd have to face the wrath of the intact US Pacific Fleet.
  • They'd hand the US a golden opportunity to destroy the IJN piecemeal.
  • All their fleet carriers are out of the first months of the war.

To keep this away from a "what if" answer, I'll lay out the problem in more detail in comparison to the already audacious Pearl Harbor attack, and its knock-on effects even if successful.

The Fleet

First, let's have a good look at the fleet which attacked Pearl Harbor. It wasn't just a few carriers, it was ALL their fleet carriers. And they needed a large support fleet of battleships, cruisers, destroyers, submarines, tankers, and supply vessels. This will become very important because of the range involved.

The submarines were for long range scouting and screening. The destroyers for short range and anti-submarine work. Their surface protection was paltry against the US fleet.

Getting There

Tokyo to Pearl Harbor is about a 7500 nmi round trip... in a straight line. The Japanese took a circuitous route, avoiding shipping lanes, to avoid detection on the way out and back. All in all it took them 28 days.

Tokyo to Panama is twice the distance and twice the time. As we'll see it's likely 20,000 nmi to avoid detection and over two months in transit. Just getting there will be a serious challenge.

How Do You Get There Undetected?

Twice the time in transit means twice the chance of detection. It means twice the chance of someone screwing up and sending a radio message. It gets worse.

Let's start by looking at the shipping lanes at the time.

enter image description here

On their way to Pearl Harbor, the fleet took a northern route weathering rough winter seas to avoid major shipping lanes. They kept radio silence for two weeks and had a screen of thirty submarines.

enter image description here

But getting from Tokyo to Panama requires crossing sea lanes, there's no way around it. The fleet certainly won't risk traveling between Hawaii and the US West Coast. It must move through the island-dotted Central Pacific where it's at risk of being spotted by any number of merchant ships moving between the Americas and Asia.

I've estimated the distance using the Great Circle Distance going from Tokyo, Japan -> Majuro Atoll, Marshall Islands -> Pape'ete, French Polynesia -> Panama City, Panama at nearly 10,000 nmi one way. So 20,000 nmi round trip. Plus zig-zagging to avoid submarines on the return.

How Do You Fuel All That?

The vessels in that fleet have ranges from 5000 nmi (destroyers) to 10,000 nmi (some of the carriers, and both battleships) to 15,000 nmi (submarines). With a round trip of at least 20,000 nmi due to the Central Pacific route, that means refueling at sea. A lot.

Fortunately the IJN knew how to refuel even in heavy seas, something the US thought only they could do, but it's always a risky proposition. They did it for the Pearl Harbor attack, but to get to Panama means twice the number of refuelings, twice the risk, and twice the number of oilers.

And they had to do it all in radio silence lest they be detected.

Unfortunately Japan was so sorely pressed for oilers they impressed merchant ships for the role. All 8 tankers for the Pearl Harbor fleet were impressed merchant ships. To get to Panama they need to find 8 more or leave half the fleet at home.

Since the canal locks are a smaller target than the sprawling naval base and fleet at Pearl Harbor, it's possible they would leave half the fleet at home. Perhaps the two shorter ranged Zuihō class carriers making them available for other strikes at the start of the war.

The Attack

Our fleet has, somehow, safely arrived undetected and is now a few hundred miles from the Panama Canal. Now what?

The Defenders

The US was already well aware that the Canal was a target and had significantly beefed up their defenses, even against air attack... but it was incomplete on Dec 7th.

For defense against surface attack, the Canal was defended by heavy coastal defense batteries that would give a Kongō class battlecruiser a seriously hard time. So no surface attack was likely. As at Pearl Harbor, it would be from the air.

The Pacific end of the Canal had an SCR-271 radar set, the same at Pearl Harbor and the Philippines. While it successfully detected Japanese air attacks on Pearl Harbor and the Philippines, it was so poorly understood and poorly integrated into the air defense that the detection was ignored. There's no reason to believe it wouldn't also happen in Panama.

enter image description here

For air defense, Panama had 24 Pursuit planes, mostly P-36 Hawks and P-40 Warhawks. These are the same aircraft as Pearl Harbor, and both inferior to the Japanese Zero. As at Pearl Harbor, they'd probably get caught on the ground. They also had various anti-aircraft guns, definitely the 37mm Gun M1, but it was deemed inadequate.

Only two detectors were installed and in operation in the Panama Canal Department. The harbor defenses had less than one complete manning detail available. The anti-aircraft artillery had insufficient personnel to man the armament being installed in the Canal Zone and only enough ammunition for one minute of fire per gun for the 37-mm. guns. There were no barrage balloons.

There's no reason to believe the Panama Canal defenders would fare any better than Pearl Harbor.

The Damage: Six Months

With surprise, superior aircraft, and in larger quantity the Japanese would have total air superiority. With their large quantity of strike aircraft and skill at dive bombing it's a near certainty that both locks would be hit and disabled. They could even be torpedoed. The planners of the I-400 attack estimated this would put the locks out of operation for six months.

A team of three shipping engineers studied the documents and concluded that the locks at Miraflores on the Pacific side were the most vulnerable to aerial bombing, but the Gatun locks on the Atlantic side offered a chance of causing greater damage, since it would be harder to halt any outflow of water. They estimated the Canal would be unusable for at least six months following a successful attack on the locks.

But this doesn't cut off shipping between the East and West coasts. It does mean they have to go around South America adding thousands of miles and weeks to the trip.

This also doesn't cut off supply between the East and West coasts, the US has an extensive rail system to draw on.

What About Gatun Dam?


27 Million Tonnes of Earth and Concrete Doesn't Care About Your 800 kg bomb.

(Technically that's the entire dam, not just the concrete spillway dam... just forgive me this bit of hyperbole.)

Gatun Dam holds back the Chagres River creating Gatun Lake which ships transit going from the Atlantic to the Pacific. It's a very tempting target to do longer term damage to the canal. Could a Japanese carrier air strike breech the dam?

No. It's not like in the movies... unless that movie is Dambusters. Damaging a dam is really hard. Bombing a dam is even harder. Why? Looks easy. Just look at that huge target!

enter image description here

The problem is if you just drop a bomb on a hard surface, like the armor of a ship or a concrete dam or the ground, most of the explosion simply reflects into the air. The Allies found this much to their annoyance trying to damage the much smaller U-Boat Submarine Pens.

To do more than chip at it you have two options. First is to penetrate deeply before exploding. Then the force of the explosion is fully transmitted to the surrounding concrete. The Allies developed bombs like the 5400 kg, 6.4 meter long Tallboy. Cast from a single piece of high tensile steel, it had to be dropped from 5.5 km to allow it to reach terminal velocity and penetrate 5 m of concrete delivering 2400 kg of extremely potent Torpex explosive.

The Japanese had nothing like this in Dec 1941, nor could a carrier bomber carry it. The closest bomb they had was the 800 kg Number 80 designed to take out small bunkers. It was capable of penetrating 0.4 m of concrete, not even enough to bury the 2.8 m long bomb, and delivered 380 kg of Shimose Powder. A B5N torpedo bomber could carry one.

But a dam wall is practically vertical, so the bomb would hit it at a high angle and just skip off.

The second way is to press the bomb against the dam underwater and then explode it. Water is incompressible and so the explosive shock will translate to the concrete. The trick is to get it right up against the dam, otherwise that same incompressible water will shield the dam from the blast. This is why depth charges had a "kill range" measured in meters. This is further complicated by the presence of torpedo nets (I'm not 100% sure the dam was covered with torpedo nets, but the locks were) which will also stop a bomb or torpedo moving through the water towards the dam. WWII bombing techniques, even dive bombing stationary target, was not accurate enough.

This was solved, after much work, for Operation Chastise aka the Dambusters raid. It used a special spinning, bouncing depth charge called Upkeep that could skip across the water, hit the dam, roll down it, and explode at the bottom right up against the dam.

enter image description here

The Japanese had no such bomb, didn't have the aircraft to carry it, and didn't have the expertise to develop it. Upkeep weighed 4000 kg and delivered 3000 kg of Torpex. Japanese carrier based bombers were limited to 800kg. Japanese overlooked anti-submarine warfare, much to their great loss, and their depth charges stank. The available Type 1 Number 25 air dropped depth-charge carried just 140 kg of explosive.

...but a spillway gate might care about a few torpedoes.

Torpedoes were an option, if there were no torpedo nets. Not the dam itself, but the metal gates at the top used to control the water were vulnerable. During the Korean War, Hwacheon Dam was attacked by bombs and torpedoes disabling the gates.

This won't produce a catastrophic failure, but it will make the gates inoperable and might flood the lake causing additional problems and more things to fix.

Getting Home

The IJN kicked the hornet's nest. Now they need to get home.

If they're smart they refueled just before the attack, but now they're over 8000 nmi from home and will need to refuel at least once, probably twice, slowing them down and making them vulnerable.

After Pearl Harbor they left a shattered US Pacific fleet behind them, but still the US Navy searched. After Panama they have the intact and superior US Pacific fleet in front of them. And the US admirals are drooling at the opportunity they've been handed.

Tsushima Reversed

When faced with a fleet of roughly equal power to their own, a commander will try to attack it piecemeal. During WWI both Britain and Germany tried to trick the other into splitting their fleet so each piece could be overwhelmed. The Japanese, looking to repeat the success of Tsushima, had Kantai Kessen which would whittle the US fleet down with submarines and air attacks as it raced to defend the Philippines.

Now the Japanese navy had split itself. Its carriers, with an inadequate surface screen, were 8000 miles away from the rest of their fleet and busy kicking off the rest of the Pacific war. They'd be slowed by their merchant oilers and their need to conserve fuel for the long journey home. They'd been at sea for a month possibly needing repair.

The bulk of the US fleet would wait while US submarines, destroyers, and long range maritime patrol aircraft searched for the returning Japanese fleet. And the Japanese would have no choice but to run this gauntlet. Once found, it would be their turn to be whittled down.

The primary target for these attacks would be not the warships, but the oilers. So far away from home, the US knew they would need to refuel. Attacking the slow, vulnerable oilers would leave the Japanese fleet low on fuel. They'd have to slow, reduce their zig-zagging, and take a more direct and predictable route home giving the US more opportunities to attack. The US Pacific Fleet would serve to block their path.

Finally, with the Japanese fleet harried, damaged, low on fuel, and reduced, the intact US Pacific Fleet of 9 battleships, 20 cruisers, 3 aircraft carriers, and dozens of destroyers would attack and destroy the cream of the Japanese Navy.

Was It Worth It?

Hell no.

This is what the Japanese had left ready to fight on Dec 7, 1941.

  • 3 light carriers
  • 8 WWI vintage battleships (2 each of Kongō, Fusō, Ise, and Nagato)
  • 16 Heavy Cruisers
  • 19 Light Cruisers

And this is what the US Pacific Fleet had.

  • 9 Battleships (some WWI)
  • 3 Fleet Carriers
  • 12 Heavy Cruisers
  • 8 Light Cruisers

With the Canal knocked out it would slow, but not stop, the flood of ships from the Atlantic including 3 battleships, 2 fleet carriers, and any number of cruisers.

With the Japanese Navy taking on both the US and British navies, this would be sufficient to defend the Philippines leaving the US with a base deep in Japanese territory. The Pacific War would go down something more like expected in War Plan Orange.

Primary Sources

Secondary Sources

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – T.E.D.
    Nov 6, 2016 at 17:53
  • 1
    @Schwern - No, I was thinking of the I-351 class submarine. Mar 28, 2017 at 18:49
  • 3
    Note also that the route taken was specifically chosen to take advantage of the fog at those latitudes at that time of year. The much more southerly route to Panama would not have given them that additional cover.
    – user18963
    Nov 21, 2017 at 22:44
  • 1
    In re-reading, an additional point comes to mind. The U.S. had good information on when the fleet carriers arrived in and departed port in Japan. Disappearing completely for a period > 3 or 4 weeks really narrows the possible targets, because very little of strategic importance is that far from Japan. Dec 22, 2017 at 15:31
  • 1
    @DJClayworth My numerous acknowlegments of your descriptive linguistic assistance. I will correct the offending passage forthwith.
    – Schwern
    Jan 3 at 19:33

The Canal is 8400 miles from Tokyo, compared to 4000 miles for Pearl Harbour. The Japanese carriers are stated of having a range of 10,000 miles at a cruising speed of about 16 knots, but remember that drag varies as the square of speed. Under battle conditions at speeds approaching 30 knots range would have shrunk to barely a quarter of that.

For a mission that far east of Pearl one must consider the entire sail back as being under battle conditions, potentially requiring not only a refuel upon approaching the target but 3, 4, or even 5 refuels on the way back, depending on how close to Pearl one dares venture. (Note that the great circle route from Panama to Tokyo goes right over Pearl.) Those tankers barely achieve 16 knots, so must be wandering around in the Eastern Pacific for a long time before and after the attack. To destroy this carrier force all that is necessary is to destroy one of the refueling flotillas.

Plus, the entire return mission probably needs to be performed under radio silence - note how a single poorly timed radio message ended the Bismarck's career earlier that year.

Couple the dangers of the mission with the difficulties of destroying, or even significantly damaging, the locks and gates of the canal, and the chances of the attack being successful are very low.

One note - it is probably better to sink vessels in the canal locks, turning them into sunken hulks, rather that the locks themselves. Several such sinkings would disable the locks for some time with a far better success rate than directly attacking the canal infrastructure.

This map of the North Pacific from Tokyo to Panama (red x's) shows a likely route from Japan to Panama that attempts to stay away from U.S. (and friendly)possessions. The busy sea and air routes from Vancouver and San Diego (and thus also San Francisco and Los Angeles) to Pearl are enclosed by the black lines. Note the distance, and thus time, spent east of Pearl.

Any attempt to approach Panama through the South Pacific is almost 3,000 miles longer, with consequent additional fuel requirements, plus the additional danger of being spotted wandering through Polynesia and Micro-/Mela-nesia while being hunted.

The actual attack on Pearl was launched while the Japanese carriers were somewhat west of the northernmost black line, about half way between its intersection with the blue line and Pearl.

enter image description here

  • 5
    One note - it is probably better to sink vessels in the canal locks, turning them into sunken hulks, rather that the locks themselves. I had similar thoughts but rejected the idea. The Panama Canal at that time had 2 or 3 lanes of locks. I do not know if all those lanes were ever in use at one time, but I doubt it. If at least 1 lane remains open, your attack basically accomplished nothing. Even if you wanted to, you would need precise intel on exactly when and what ships were using the Canal at the right time. I don't think that's feasible for planning a strike 8000 miles away.
    – DrZ214
    Nov 6, 2016 at 3:54
  • 1
    +1 for the rest of your details. I'm making an edit to the OP because I recently discovered the Gatun Dam, a hydroelectric dam that provides electricity for the locks. Destroying the dam alone might put the whole thing out of business for half a year.
    – DrZ214
    Nov 6, 2016 at 3:55
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    @DrZ214: The Japanese never had the technology to successfully breach a large dam from the air (en.wikipedia.org/wiki/Operation_Chastise): "Wallis's breakthrough was to overcome this obstacle. A drum-shaped bomb — essentially a specially designed, heavy depth charge — spinning backwards at over 500 rpm, and dropped at a sufficiently low altitude at the correct speed and release point, would skip for a significant distance over the surface of the water in a series of bounces before reaching the dam wall.". Nov 6, 2016 at 4:21
  • I'm not sure I can believe that. A dive bomb attack using simple but large depth charges, set to detonate at a certain depth, could almost surely have gotten the job done. I thought the spinning bouncing bombs were invented to let the pilot release at a distance and not get too close to the Dam and the AA guns there. Alternatively, you could torpedo bomb the Gatun Dam. But I do not know how big or thick that Dam is. Wikipedia describes the Gatun Dam and an "earthen dam" or "embankmen dam", but does not specific its exact construction.
    – DrZ214
    Nov 6, 2016 at 4:36
  • 8
    The Gatun Dam is almost 400 metres thick at water level, and seem to be larger than any of the dams attacked in Operation Chastise. The point of the bouncing bomb was that it bypassed anti-torpedo nets in the reservoirs, but it was also large, at 9,250lb, with 6,000lb of explosive. The Japanese carrier-based strike aircraft are limited to much smaller loads. I think this dam is probably too big for them to destroy. Nov 6, 2016 at 10:02

Destroying those locks is going to be harder than you think. They are very large, at 110 feet x 1,050 feet, and the lock gates have to have been built to stand up to accidental collisions with large ships (at low speed, admittedly). They weigh up to 730 tons, depending on their height.

The best way to make the attack seems to be to use anti-ship torpedoes to attack the lock gates, dropping them into the locks, or the canal outside the locks. This needs to be done in a carefully organised way, because if one lane remains operational, the canal is still very useful.

Edit: The reason for using torpedoes is that they make it relatively easy to get an explosion in contact with the lock gate, which is hollow and can thus be flooded and made immovable until it is repaired and pumped out. Doing that with dive bombing is chancy: aviators always overstate their accuracy, and dive bombers could often miss ships entirely.

The correct gates to attack seem to be the downstream gates at the Pedro Miguel locks. Here, there is only a single lock in each lane, so there's less scope for aircraft attacking the wrong gate. You want to hit the downstream gates because there are two sets of upstream gates in each lane, as a precaution against floods.

If the downstream Pedro Miguel gates are destroyed, the canal remains usable, for smaller ships, because of the auxiliary gates half-way along each lock. Since those are normally retracted, attacking them is much more difficult.

The Japanese had the ability to refuel at sea, so they could have got some ships into position to make that attack. They probably could not have staged the entire Pearl Harbour task force out there, but nor would it have been necessary. The defences of the Pacific end of the canal don't seem to be all that strong. There is an infantry regiment, a coastal artillery regiment and an additional artillery battery. The Air Corps had a composite wing with 28 medium and 14 light bombers and 24 fighters.

The big risk of the mission is getting the attack force back afterwards. It will be thoroughly clear who has made the attack, and an intact US Pacific Fleet at Pearl Harbour is in an excellent position to cut off the Japanese force and destroy it.

I don't think the Japanese would have given the canal high enough priority to take that risk, given its limited practical effect and that they always concentrated on attacking military forces and neglected attacks on USN logistics throughout the war.

Edit: I also don't think they would have thrown away a pair of carriers (you need to send two so that an accident doesn't abort the whole mission) and their escorts and aircrew as the opening shot of a war. They didn't engage in suicide tactics until they were clearly loosing and the situation was desperate.

  • 5
    Yes, the return trip might be the biggest risk. After the surprise is over, it's still a long way back home. I had ideas of a full kamikaze attack, where even the carrier goes on a one-way mission. That would keep the force small, allowing a simultaneous and much larger attack on Pearl Harbor. Pretty ambitious, but if we're gonna use hindsight, might as well use it all the way. +1 for the details. Only 24 fighters at Panama Canal? Do you have a source? I wanna make sure this is the force that existed as of 1941 Dec 7. I also wanna know what AA guns, including flak guns, might be there.
    – DrZ214
    Nov 5, 2016 at 14:41
  • 1
    BTW, the reason I thought the locks were so vulnerable to simple bombs is because I researched torpedoes of WW2. This led me to understanding that the best torpedo explosion is underneath the ship, not impacting the side of the hull. The shockwave in water is pretty powerful. But it looks like those locks were very thick and strong.
    – DrZ214
    Nov 5, 2016 at 14:43
  • 2
    Edited responses to those points into the answer. Under-hull explosions are indeed more damaging, but making them happen reliably was a little beyond WWII technology. Most effective torpedo attacks during the war were hitting the side. Nov 5, 2016 at 15:07
  • Thanks but that link does not appear to have info on AA guns. Speaking of torpedo attacks, I just checked the map and the Pacific Locks appear too embedded in the gulf for a traditional sub attack.
    – DrZ214
    Nov 5, 2016 at 15:26
  • No, I haven't found any info on AA guns yet. Trying to sneak a sub in there does look hard. Nov 5, 2016 at 15:27

Canal locks may be much harder to destroy than you think. Ships can catch fire and they can sink. Canal locks won't do either.

As kind-of-evidence for this assertion, consider the St. Nazaire Raid. The Allies decided that they'd have to ram the gates of a dry dock with an explosives-filled destroyer. At the time, they had much heavier aviation at their disposal than the Japanese Navy.

You might also consider the Dambuster raids for a similar target.

  • Probably the Japanese would not have targeted the locks themselves, but instead attempt to block the canal by sinking sh8ps at the Pacific entrance to the canal. It would have only delayed the transfer of Naval vessels to the Pacific Fleet, but the purpose of the Pearl Harbor attack was also to delay the USA's ability to respond. Mar 28, 2017 at 18:16

Destroying the Panama Canal would have been extremely difficult and provide limited benefit. Many historians believe the Japanese wrongly targeted destroyers and battleships at Pearl Harbor, mostly due to the fact they thought they would play a more important role than submarines and aircraft carriers. They even neglected to disable the naval repair yards and oil reserves, which proved fatal, as the Pacfic Fleet was repaired in record time and faced no oil-supply shortages after the attack.

Attack on Pearl Harbor: Strategic Implications

  • 1
    If that's true "why use Aircraft Carriers." And I'll tell you why..."the Old Fogies at running the US Navy hated Aircraft Carriers...and Submarines too." So the simple solution to this problem is... Nov 8, 2016 at 17:31

The Japanese weren't "out" to destroy the Panama Canal. More to the point, they weren't even out to destroy Pearl Harbor (although they could have done so, in effect, with follow up attacks on the docks and fuel tanks).

What the Japanese wanted to do was to destroy or "cripple" the U.S.Pacific fleet, thereby setting back America's war effort by two years. And this fleet lay at Pearl Harbor, which is why Pearl was the target. By the time the U.S. fleet was rebuilt in mid to late 1943, Japan hoped to have completed its defense perimeter, including Midway, and the Fiji, Samoan, and New Caledonian Islands off Australia. They actually got about 90% of what they wanted.

They didn't count on American "persistence" (the main Pacific effort didn't begin until the fall of 1943, on the Japanese timetable). Nor did they expect America to get a "head start" by waging a war of attrition in the year before then.

As other posters have pointed out, the Panama Canal was twice the distance (or more) from Japan as Pearl Harbor. Destroying it without "catching" the American fleet would have been a highly risky affair for the Japanese fleet on the way back. Instead, Japan actually achieved most of its "stated" goal at minimum risk.

  • 1
    The fleet at Pearl was not the whole US fleet. There was also the Atlantic Fleet. In the event of war with Japan, Japan could expect the US to reinforce its Pacific Fleet with portions of its Atlantic Fleet and thus be outnumbered. Plus troops, supplies, and support vessels would all use the Canal to supplement existing rail lines to supply the Pacific War. The US's two-ocean navy was a serious problem for Japan, and they did not plan on Germany declaring war.
    – Schwern
    Aug 18, 2017 at 0:35
  • @Schwern: The U.S. had 15 battleships, and 6 aircraft carriers between the Atlantic and Pacific. The Japanese had 11 battleships and 11 aircraft carriers (they were allowed 9 of each under the 5-5-3 treaty but they overbuilt their quota). Six battleships were put out of action at Pearl. That left 9 battleships and 6 aircraft carriers in both oceans against 11 of each for Japan.
    – Tom Au
    Aug 19, 2017 at 7:04
  • @TomAu The USN actually had 17 battleships in commission at the time, although I'm not sure how battleworthy the newest two were at that time. Aircraft carriers were not restricted by number in the Washington Naval Treaty, but by total displacement tonnage, and the Japanese had built additional ships after renouncing the treaty. All battleships at Pearl Harbor were damaged to some extent, but four were ready for battle fairly shortly, leaving two as complete losses, one rejoining in late 1943, and two in 1944. Dec 5, 2018 at 17:00

A successful attack on the Panama Canal was possible but under different circumstances and without the need Japans carriers.

Using a seaplane tender, with up to six Mavis flying boats could put the Panama Canal out of business for two-three years.

The Chitose, could leave from Kwajalein Atoll, Japanese territory. One ship, it would have to cross shipping lanes, but the trip would be half the distance than from Tokyo. At the same time, an oiler would leave, slightly different route but with a rendezvous schedule, to fuel up.

Any merchant ship seeing another ship, on the distance, is going to change course. The Chitose would do the same. Another merchant ship wouldn’t get close enough to identify it. This process was done to avoid German commerce raiders. They could go months without being seen, so it’s possible the Chitose could as well. If not, its actions would make it look like it was trying to stay away from another merchantman.

The Chitose sails to the Galápagos Islands. Even if seen, it’s a single ship, travelling the ocean. If identified, it’s peacetime.

The Mavi flying boats are painted like they are Panam flying boats (Mavis’s looking a lot like Panama flying boats) The Mavis flying in on differing routes to Panama, in early afternoon or otherwise same time as attack was heading in on Pearl. Three of the Mavis target the Gatineau Dam spillway gates. The other three target the Madden Dam. Two of them are loaded with high explosives. They land on the lake, right up against the dam, use scuttling charges to sink em next to dam, with timers. They sink, charges are set off taking out that dam. Water floods Gatun Lake, while the Gatun Dams spillways are damaged.

Some further info

  • There were 3” aa guns at Gatun Locks, right next to the dam
  • They were in revetments that prevented them from firing at too low a target. There was a shortage of crews, only 1 minute of ammo & crews weren’t well trained.
  • The only radar working was the same as at Pearl & was at Pacific Ocean end. But, Pacific Ocean end was actually EAST of the Atlantic side. The mountains in southern Panama could obstruct the radar. Even if sited, they could be confused with Panam flights.
  • Any patrol aircraft would probably be few, if any. First cuz it’s a Sunday, second cuz it’s early afternoon, not when an attack would be expected, third, it would be done by small individual aircraft not a massed swarm as would be expected, fourth, the aircraft would be under false colours and I’d seen wouldn’t likely be attacked
  • At the time neither high command, or Pearl Harbour have issued an alert and no long range patrols have sited any issues
  • At the time there were no torpedo nets protecting the dam spillways
  • Bombs Or torpedos would only inconvenience the lock gates at best

In December, with losing all that water from BOTH dams would have put canal out of business for two to three years, per high commands estimates.

Shipping rail traffic from east coast to west coast wasn’t much of an option. During wwii, USA expanded all ports on west coast considerably. As it was ships were waiting in port for three weeks before they got their turn to load up. Without the canal it would have been double that That leaves going around Douth America. In 1942, 1943, there was a severe shipping problem, merchantmen going around the Horn would have exposed merchantmen in the Atlantic to U Boats. That would have meant going in convoy which would have even worsen the shortage of shipping. Some merchantmen would have been lost going around the Horn. All operations in the Pacific would have suffered delays unless significant ships had been devoted which would have affected the war in Europe.

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  • Gatun Dam is a much harder target than the Operation Chastise dams. It's an earthfill dam with a gravity-dam spillway, where the Operation Chastise targets were gravity-arch dams. Additionally, an H6K can only carry about 3000kg of cargo, versus the 4100kg of the bouncing bombs.
    – Mark
    Jan 6 at 4:06

I think the Janpanese could have used a merchant ship in disguise loaded with tons of explosives. They would enter the canal and blow the whole thing just at the locks, destroy the locks and block the canal. Maybe they would use 2 or even 3 ships. This would simply avoid all logistic problems of a large navy raid and keep their naval battle force instact. No chance for the US navy to catch anything on the retreat...Just think St.Nazaire a little bigger.

  • 1
    This would benefit from sources. As stated it appears to be opinion. I suspect such an action would have been illegal.
    – MCW
    May 8, 2017 at 13:46
  • 2
    @MarkC.Wallace: Yes, it would benefit from sources, and yes it appears to be opinion. But... illegal? Like in, more "illegal" than the attack on Pearl Harbor?
    – DevSolar
    May 8, 2017 at 13:55
  • 1
    Attack on Pearl was military ships on a military target. Attacks out of uniform are generally illegal. IANAL; my point was to highlight the difference between a researched answer and a simple opinion.
    – MCW
    May 8, 2017 at 14:08
  • 3
    @MarkC.Wallace If Imperial Japan demonstrated anything quite clearly, it's that they didn't care about legality. Naval tradition (not sure about international law) is full of false flag operations; so long as they hoist their true flag before opening hostilities.
    – Schwern
    Aug 18, 2017 at 0:19
  • 3
    Though I don't have specifics on their search procedures, the canal zone was already on high alert for sabotage. Something as obvious as an exploding Japanese merchant ship would be unlikely to succeed, if they were allowed to use the Canal at all. It would also be suicide for the crew. While later Japan would employ suicide as part of their plans, they were not doing so in 1941.
    – Schwern
    Aug 18, 2017 at 0:27

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