Why did carrier battle groups require multiple carriers?

Question

During the Pacific War, both USN and IJN operated (or at least preferred to) carrier battle groups composed of multiple carriers plus their screening ships. IJN's Kidō Butai - which carried out the assault on Pearl Harbor - consisted of 6 carriers. Late in the war, USN mainly operated Fast Carrier Task Forces, which were composed of multiple task forces of 3-4 carriers each plus their escorts.

During the inter-war period when people weren't familiar with how to use carriers, the USN operated single-carrier groups. Fleet Problem XIII exposed weaknesses with this setup, and recommended more carriers per group:

The exercise showed that one carrier was insufficient for either fleet attack or area defense, so the practice of two or more carriers operating together became policy. Admiral Harry E. Yarnell said that six to eight carriers would be required for a Pacific campaign, but no orders were placed for new carriers, as Depression-era financial difficulties caused President Herbert Hoover to limit naval expenses.

Later when supercarriers appeared and after the post-war drawdown, the USN reverted to the single-carrier carrier strike group which persists today.

My question is: why did WWII-era carrier battle groups require multiple carriers? And why did the USN go back to single-carrier groups? Was it:

• Putting enough planes in the sky
• Eliminating a single point of failure, the carrier
• Cost

Answer 1

Fleet Problem XIII highlighted the problem of having a single carrier in an attack flight - Saratoga was "sunk" during the exercise, and the attacking Blue fleet lost any air cover which allowed the defending Black fleet, which still had the Lexington, to attack the remaining battleships and other vessels of Blue fleet.

Also, another exercise (Grand Joint Exercise No 4 - which, incidentally, incorporated Sunday morning air raids on the Army airfields from an invading fleet), demonstrated how the two carriers (Saratoga and Lexington) provided mobility and support (Lexington was able to recover Saratoga's planes after the latter's deck was rendered "inoperable").

Fleet Problem XIII & Grand Joint Exercise No. 4:Reconsidering Aircraft Carrier Doctrine

Surprisingly, despite the big difference between the displacement of a super carrier (Enterprise is about 90,000 metric tons) and a WWII era vessel (Lexington was 33,000), the air wings' sizes are roughly the same (up to 90 planes on the Enterprise, and about 80 on the Lexington). I would have thought the smaller ship would allow fewer planes, limiting the strike power. On the other hand, the planes of today have a much stronger strike capability.

As for the change in doctrine - the single carrier group came about almost right after the end of the war, as the military began being drawn down. The obvious reason is cost. But the other reason is that no other nation had a comparable Navy. Add the multi-role capabilities of the super-carrier and developments in anti-air and missile strike technology, and you don't need to follow the same doctrine as in WWII.

Answer 2

Do not confuse world war with peace time. Even though during the cold war there were military actions, the magnitude is not the same. During WWII USA built almost 100 carriers of many sizes, while in the cold war usually only 12 big carriers were available.
During cold war, USA actually used several carriers at the same time in a single theater whenever it was required. For example in the Gulf War, where several carriers were in the Red Sea.
In the present, since USA has many interest worldwide, they must keep military presence in many places, as result they divide their forces in all oceans. While in the WWII their influence was inferior, because many seas were covered by the Royal Navy. As result its ships where concentrated in less oceans.

Answer 3

A carrier strike group consisting of a single carrier is a peacetime construct. This is enough for patrolling and "power projection" purposes. The U.S. Navy has basically been at "peace" since the end of World War II (some land bombardment in the Korean War, but no naval battles), and of course, during the Interwar period.

Groups with multiple carriers formed up in World War II because reserves were needed against enemy "first strike" capabilities. Hopefully, a U.S. fleet wouldn't lose all of its (multiple) carriers at the same time. My guess is that we will see a return to multi-carrier groups if there is another major (naval) war.

Answer 4

the WW2 carrier was not as we now have a multi role carrier. Each carrier had a specific task, be it air defence, ground attack, ASW, etc. etc.. Therefore a task force that had more than a very limited role would have multiple carriers assigned to it, at least one for each role requiring aircraft. An amphibious assault group for example might have a strike carrier and an air defence carrier. A convoy crossing the Atlantic would have an ASW carrier and maybe and air defence carrier as well (though most didn't, adding a small complement of fighters to the ASW carrier as chances of meeting hostile aircraft were limited).

For larger operations where the number of aircraft in a single carrier's complement would be too small for the task, multiple carriers would be assigned to a single task force.

That has not changed by the way. During Desert Shield/Storm multiple carriers were assigned to the operation at any one time. Same in Vietnam where at least 2 carriers were on station at any time and during peak periods 3 or even 4 were assigned.