Here is a link to the missions undertaken by the USN subs, for transport type missions
WWII US Submarine Special Transport Missions in the Pacific During World War II 1941 to 1945
Now, as you can see, there are a lot of missions undertaken, and some involving quite large numbers of people. However, there needs to be word of caution thrown in. Firstly, the evac missions are not comparable to a commando raid, because they would be unlikely to involve a large amount of stores and equipment, and secondly so long as you get your evacuees out alive, the mission is a success...it doesn't matter what state they are in when they disembark, so long as they are OK.
Now, we should also compare the available hardware, of both the German Navy, and the USN. As you can see, a lot of the missions were undertaken by regular USN fleet boats, which typically were the gato class. These boats had a deep load displacement of 2400 tons, so were quite large in comparison to the German counterparts. But perhaps it is best to look at the two "commando" subs, the Nautilus and the Narwhal, and specifically compare them to what might be available to the Germans.
Nautilus and Narwhal were quite old subs, but they were unique in that they were designed as mine layer. They reportedly were designed to carry up to 200 mines II RC. They were huge boats as well, with a deep load displacement of over 4000 tons. This enable them to carry a full company (less one rifle section) per boat, so that for the famous raid on Makin in August 1942, the two boats were able to land 211 men, and over 30 tons of stores, but only after they had been converted to the purpose. This conversion took about 4 months to complete, from Pearl Harbour through to some time in April. From that point until the actual operation, the Boats and the commandos were in training, although the actual target was not finalized until June.
Finally, it is worthwhile to take note of the actual time spent at sea, the boats cleared PH 9 August, spent two days on station, and returned to PH 26 August. Total Mission time was 16 days, and total sea time was 14 days
Now, lets compare that to the likely German capability. Sorens suggestion is that the mission takes place early 1942, and that it would involve about 30 commandos. He has not stated the amount of cargo being hauled, but from the looks of it, it could be conservatively estimated to be about 30 tons.
Now if the mission is to take place in early 1942, it immediately rules out using the biggest of the German boats, the Type IXD2, because these were not ready until later in 1942. Moreover, they would have needed some time to be made suitable for this purpose, as we have see, it took the American 4 months to convert the Nautilus and Narwhal, so it seems reasonable to estimate that the Type IXD2s would not be ready until the end of 1942, at the earliest. So this mission, in order to be carried out at the times designated would necessarily have to rely on one of the earlier types, most likely a Type IXC. These boats have a deep load displacement of 1200 tons, so, on a straight comparison of displacement alone, they are going to be able to carry about 32 troops. However, the difficulty with this, is the mission time. To complete the German mission, the total mission is going to be about 33 days, 14 days outbound, 14 days return journey, and Say about seven days at the target. If the troops are to arrive in any sort of combat capable state, the numbers per boat will have to drop. having spent time on a submarine, they are a most uncomfortable means of transport. If you apply the rule of thumb, and apply the mission time to a range to payload equation, you arrive at a carrying capacity per boat of about 16 troops per boat. Now that means a minimum of two boats to complete the mission.
On top of that you need to consider the down time for the boats themselves. Based on the US experience, it would take about 4 months to make the conversion, and another 3 months to train for the mission, and then another say two months to return the boats to normal operations. And there is also the mission time itself. All up your two boats are unavailable for other missions for at least 10 months, a massive cost in the tonnage war.
Missions of this type are certainly possible. The Australians undertook two extremely daring anti shipping missions into Singapore harbor, the most famous of which involved the use of a small trawler, the MV Krait. These raids cost the Japanese over 40000 tons of shipping, but required many months of advance planning to implement.
For the Germans, I think a far more cost effective approach would be to engage in an intensive mine laying campaign in the Caribbean by as many blockade runners as they could lay their hands on. Even a modest mine laying campaign would have disrupted the movement of vital fuel oil for months, and caused serious dislocation to Allied economic development. And at no cost to the all important tonnage war, which had to be pursued relentlessly, if there was any hope of winning in 1942.
For those interested in the Carlson raid, here some good links as a start
From Makin to Bougainville: Marine Raiders in the Pacific War (Makin)
Historical Reflection
For those interested in the correct way to approach commando style operations , I recommend having a second look at the operations of the Krait. Here are some links which i think are interesting:
MV Krait - Wikipedia, the free encyclopedia
Two Events of 1943
I also recommend the following written publication
Subs Against the Rising Sun: U.S. Submarines in the Pacific, Keith H. Milton, Yucca Free Press, 2000
), but more about the ones in service in the 70's and up until the early 90's, and can tell you for a fact they were definitely no more roomy!
