What was the longest a World War II submarine stayed at sea without being resupplied at a port?

Question

The US Balao-class and Gato-class submarines had enough provisions to stay on patrol for 75 days under normal operating conditions. Information on other long-range submarines has proved hard to find, although this site mentions that British O, P and R class submarines had a range of 20,000 miles, but there is no mention of actual or possible duration at sea without being resupplied. What I am looking for here is the longest period submariners went without being able to set foot on (friendly) land.

The US navy had submarine tenders (supply ships, nod to justCal's comment) which could supply submarines at sea, which opens up the possibility of greatly increasing the aforementioned period of 75 days for some US subs. The Germans also had at least one submarine tender, the SS Saar, which was operational throughout the war. Thus, submarine crews could have remained at sea for extended periods during WWII without being able to set foot on land for some R & R.

What is the most number of days that a submarine remained at sea during WWII without going to a port to be resupplied (but which may have been resupplied at sea by supply ships)?

Also, were there any submarines of other navies (British, German, Japanese, Russian) which could stay at sea longer than this (75 days) without being resupplied? By 'could', I mean under relatively normal operating conditions (i.e. without the crew resorting to such extreme measures as drawing of straws / cannibalism, as suggested by Scott's comment).

Answer 1

Not a "hard" answer, but more than a comment.

The German Type VIIC was the most common type of U-boat, but with limited range and endurance. Its fuel bunkers could keep the diesels going for 20-35 days non-stop at a speed of 10-12 knots (own calculation, using the various "range X at speed Y" data points given here and here).

The Type IXC/40 would, by the same token, have fuel for 57 days at 10 knots, non-stop.

We know from various sources (e.g. "Das Boot", Lothar-Günther Buchheim) that U-boats would "patrol" their designated areas at much slower speed, to conserve fuel. Stopping the boat for maintenance and repairs would further extend the solely fuel-based equation, while combat operations like closing in on a convoy (when a boat would run at high speed) would decrease range drastically.

Records for the longest war patrols were 97 days for a Type VIIC (U 552) and 225 days for a Type IXD2 (U 196). After that 225 day patrol, U-196 returned to Bordeaux on October 23rd, 1943. Apparently the crew was sane, or at least fit to serve, enough to leave, after 143 days in harbor, for another war patrol that lasted 147 days.

However, it is difficult to ascertain whether a boat was resupplied at sea on any given patrol. (U 196 was part of a group of similar boats operating in the Indian Ocean, with a tender operating as supply ship and mobile base, so it's fairly safe to assume they were resupplied in one way or another.)

Answer 2

Japan built several of the I-400 class submarines, two of which, I-400 and I-401, were operational in early 1945. These enormous submarines had a 37,500 nautical mile range, over three times the range of a Gato submarine, so one can presume that crew stores would be present to keep the crew functional for a voyage of several months. There seems little point in building that sort of range into a submarine if the crew can't last as long as the fuel.

However, by the time the I-400's were operational, the war situation had changed to where the planned attacks on the Panama canal, Los Angeles, Washington DC and NYC were no longer considered to be practical.

Answer 3

The Japanese built the largest submarines in World War II (52 out of the 56 submarines) of over 3000 tons). These were also able to stay underwater the longest, over 100 days, and carried the best torpedoes. Some 41 subs carried aircraft. The reason for these innovations was that the Japanese were operating in the Pacific, the largest ocean in the world.

Despite these advantages, the Japanese submarine fleet had two problems. The first was that the Japanese built onl 174 of them. The second, and more important reason was that they were used to fight warships, not merchant ships, and also to resupply isolated Japanese garrisons, so 128 of the 174 were lost in combat. The survivors were mostly new or training ships.