WWII Submarine Forces (1939-1945)

The German Type VIID submarine U-218

Submarine warfare is an iconic aspect of WWII. However, attention has long been focused on the U-Boats of the Kriegsmarine while the undersea arms of the other navies were largely neglected. Recently, there has been growing appreciation for the effectiveness of the American submarines, but the Japanese are still widely disparaged for not using their submarines correctly and little is heard about the British or Italians at all. This post is intended to provide basic overview of the size and composition of the submarine arms of the five great navies of WWII, in order to lay the foundation for a later analysis of their wartime effectiveness.


Force Size
The following chart include all submarines that served during the war, excluding dedicated training submarines, transports, minisubs, and manned torpedoes.

What immediately leaps out is that the German submarine force was 40% larger than those of the other four navies combined - easily explaining the amount of attention it has received. The figures for the other navies are comparatively unremarkable and correspond fairly closely with their respective nations' overall naval strength during the war. However, these numbers are still somewhat deceiving as the types of submarines operated by the five navies varied considerably, from 35 meter coastal boats to 122 meter aircraft-carrying behemoths, so let's take a look at each nation in turn.


Germany

The Type VIIC submarine U-378

By far the most common German submarine was the famous Type VII, of which seven hundred and nine were built in several variants (Type VIIC being the most common). While their 67 meter length was fairly average for European boats, their endurance of 8,500 miles at 10 knots was remarkably good for their size. Speed was 17 knots surfaced, more than enough for attacking convoys traveling at 8 knots or less, while armament consisted of a 3.5" deck gun and five 21" torpedo tubes with fourteen torpedoes.

The second most important German submarines were the one hundred and ninety four Type IX boats. At 76 meters in length, with an endurance of up to 13,500 miles, and armed with a 4" gun and twenty two torpedoes, these vessels were used for patrolling areas beyond the reach of the Type VII. The final class worth noting were the fifty Type II coastal submarines. While fairly limited at only 41-44 meters in length and with an armament of just five torpedoes and no deck gun, these small boats still played an important role in the confined waters of the Baltic and off the British Isles.

While the highly advanced Type XXI and Type XXIII submarines receive substantial attention, and one hundred and seventy nine of them were built, they suffered from numerous issues that delayed their introduction to service and very few of them ever went on combat patrols.



United States

The Balao-class submarine USS Bowfin (SS-287)

The American submarine fleet was remarkably homogenous and built around the concept of a large fast "fleet submarines" that could keep up with the surface forces as they fought their way across the expanse of the Pacific Ocean. This aim was achieved with the 1938 Salmon-class, and its general characteristics were shared by the next five classes (two hundred and forty three boats in all by the end of the war). These vessels were 94-95 meters in length and capable of 20-21 knots on the surface. They had a range of 11,000 miles at 10 knots and were armed with a 3" or 5" deck gun and ten 21" torpedo tubes with twenty four torpedoes (the final twenty two Tench-class boats had improved propulsion for a range of 16,000 miles and could carry twenty eight torpedoes).

The remainder of the American undersea arm consisted of nineteen proto-fleet submarines that were somewhat inferior in all respects, but still quite capable, and forty one of the 63-73 meter S-class boats designed during WWI. With a speed of 14 knots, a range of 5,000 miles, and only fourteen torpedoes, these submarines were of limited utility in a Pacific war and were mainly kept in second line roles.



Great Britain

The S-class submarine HMS Scotsman

The British submarine force was largely composed of three classes, all of which first commissioned in the late 1930's and remained in production throughout the war. The sixty two boat S-class was designed for European waters and were of average size at 62-66 meters in length. While their speed was only 13-14 knots on the surface, they had an acceptable armament of a 3" deck gun and six 21" torpedo tubes with twelve torpedoes (some carried a thirteenth torpedo in an external stern tube) and were fairly comparable to their German counterpart, the Type VII.

The larger T-class consisted of fifty three boats and was originally intended for the Pacific. However, at 84 meters in length, with a range of 8,000 miles at 10 knots, a speed of 15 knots surfaced, and an armament of a 4" deck gun and sixteen torpedoes, it was clearly far less capable in that environment than the American fleet boats. Its intended duties were to be shared with the twenty two boats of the O, P, and R-classes, which, while older, were fairly similar in all respects. However, in actuality none of the British submarines spent much time in the Pacific.

The final group was composed of the forty nine boat U-class and its improved variant, the twenty two boat V-class. This design was originally intended as a training vessel, but the need for warships caused it to be armed and pressed into service. At 58-62 meters in length with a speed of just 11 knots, these submarines were of limited capability but could be produced in large numbers. Armament was rather poor, consisting of a 3" deck gun and just eight torpedoes (the first seven U-class boats carried two additional torpedoes in external tubes, but these caused various issues and were omitted on later boats).



Japan

I-15, the lead ship of her class - note the catapult on the bow and the extended hangar built into the sail

The Japanese submarine force was composed of a large number of small classes. However, these classes largely represented incremental improvements on two main types: Junsen (cruiser submarines - fifty three in service) and Kaidai (large submarines - thirty one in service). Japan also fielded fifty nine coastal submarines, but these were more heterogeneous in nature. Finally, there was a number of specialized vessels, including the famed I-400 submarine aircraft carriers, as well as twenty four submarine transports used to resupply besieged island garrisons.

The most common of the Junsen was the twenty boat I-15 class, which shared its general design with five other classes (twenty two submarines). These were huge and incredibly capable vessels, measuring 109 meters in length with a speed of 23 knots on the surface. Endurance was 14,000 miles at 16 knots and armament consisted of a 5.5" gun and six 21" torpedo tubes with seventeen torpedoes. Most notably, they also had a catapult and hanger for a floatplane - a feature common to the vast majority of Junsen. Those not fitted for aircraft generally carried minisubs or manned torpedoes instead.

The Kaidai are best represented by the ten boat I-76 class, an improved version of the eight boat I-68 class. While noticeably less capable than the Junsen, at 105 meters long they were still large submarines by any standard. Endurance was 14,000 miles at 10 knots and they were armed with a 4.7" gun and six torpedo tubes with fourteen torpedoes.

The most modern of the coastal boats was the eighteen submarine Ro-100 class. While designated "small" by the Japanese Navy, at 60 meters they were actually fairly average by European standards. However, with a speed of 14 knots and a range of 3,500 miles at 12 knots they were clearly second line vessels. Their armament was also poor, consisting of four torpedo tubes with eight weapons and no deck gun. The other coastal submarines consisted of twelve of the British L-class, built under license, and twenty of the older Kaichu. Both of these classes were larger (73-81 meters), faster (15-19 knots), and had 3" deck guns, but carried a similar torpedo armament to the Ro-100.



Italy

The 600 Series submarine Iride

Italy had by far the least homogenous submarine fleet of the war, consisting of several separate design branches and subbranches, as well as numerous one off classes and a small number of captured French and Yugoslavian vessels. However, the bulk of the fleet was composed of five closely related classes of coastal submarines known as the 600 Series (for their nominal 600 ton displacement). These fifty nine boats were on the smaller side at 60-62 meters in length and suffered from poor endurance, being capable of around 2200-2500 miles at 12-14 knots. Their other characteristics were likewise average at best, with a speed of 14 knots surfaced and an armament of a 4" deck gun and six torpedo tubes with twelve torpedoes.

Still, the entire Italian undersea force should not be judged by the poor capabilities of the 600 Series as, it also included a respectable number of fairly capable ocean going submarines - the most numerous of which was the eleven boat Marcello-class. At 73 meters in length, with a speed of 17 knots, and a range of 13,500 miles at 9 knots, these vessels were quite comparable to the German Type IX submarines, with the main difference being that they had two 4" deck guns but only sixteen torpedoes. Although rarely mentioned in the history books, the larger Italian submarines spent much of the war operating out of the German submarine bases in France, attacking merchant traffic off the United States and South America.