I'm learning about the capabilities of German u-boats during the Battle of the Atlantic and their improvements during the war, in the most general sense.

I researched three types of U-boat, the VIIA, VIIC, VIIC/41. (Source)

Top speed: approx. 18 knots on surface, 8 while submerged. This doesn't appear to have improved much during the war.

Range: approx. 6000 miles (at 10 knots) with the earlier VIIA, but 8500 miles with the later versions. A further improvement (the VIIC/42) was planned that could travel more than 12,000 miles, but none were built.

Armament: Early models carried 11 torpedoes, later ones carried 14. Most had some smaller arms on the deck for use on the surface only.

Torpedoes: The T1 was flawed due to its visible surface bubbles but had a fairly large range and high speed (6000m at 44 knots). Later models like the T2 and T5 had a lesser range (5000-6000m) and speed (20-24 knots) but improvements in their ability to seek loud objects and better detonators. There were 4 bow tubes and 1 in the stern. (Source)

Passive Sonar: A slow-moving u-boat (4 knots) could hear a cargo ship from 3.5-7.5 mi. away, a destroyer from 5-10 mi. away, and a large convoy up to 50 mi. away. As the u-boat increased its speed, its listening range was reduced significantly. (Source)

Radar: U-boats were fitted with radar for the active detection of ships (while surfaced), but they were either ineffective or seldom-used because of the chance of giving away their own position. (Source)

Have I grossly misunderstood any of this, or is my summary of the capabilities of German u-boats sufficient as a starting-point? Are there other, more important, capabilities that I have neglected to learn about?

  • 2
    I can't actually tell what you're expecting as an answer. Only you can determine if this information is sufficient as a starting-point because only you know what the requirements are. The problem with these "top trumps" comparisons is that the values are usually best case estimates which varied greatly in real-world usage. There are also plenty of aspects of use that aren't easily summarised into simple numbers.
    – Steve Bird
    Dec 20, 2021 at 7:01
  • research also tactical development: en.wikipedia.org/wiki/Wolfpack_(naval_tactic) And consider the importance of cannons: undefended cargo ships could be sunk by the cannon, thus saving torpedos. Thus, escorted convoys also force the subs to use torpedos, as they do not have the leisure to remain on surface to use their cannons.
    – Luiz
    Dec 20, 2021 at 17:40
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    You may wish to consider something they did not do well at all, communications security. Doenitz requiring daily reports from his U-Boats at sea made him happy, but served, even when codes were not being broken, to provide tracking information for the Allies to either avoid the submarines or, better, attack them.
    – R Leonard
    Dec 21, 2021 at 0:56
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    A uboat's deck gun was a major function of its weapon system as these submarines were all employed as submersible cruisers in the commerce raider role. The aim of a convoy attack by a wolfpack was, in part, to break the convoy to cause individual sailing, resulting in individual ships able to be deck gunned. Correspondingly during the early and mid war slow and medium speed commercial ships sailing singly were a chief target. Dec 21, 2021 at 8:46
  • Another important capability is how long the sub can remain submerged. The more, the easier to evade pursuing ships and to hide from aircraft. Plus: maximum operational depth: going deeper is not only obviously stealthier by itself, it also allows the sub to take advantage of thermal currents to hide even better (altough I am not sure if this was possible on WWII)
    – Luiz
    Dec 21, 2021 at 15:45

1 Answer 1


I'd add a few things.

Type IX long range boats

Few in number, but significant in the attacks on the US in 1942.

Type XIV "Milk Cow" resupply boats

These extended the range and durability of the shorter range Type VII's.

Number of boats, and when

Not just absolute numbers built, but operational numbers at critical stages of the battle. The Germans never had enough.

Germany started the war with just 57 operational U-Boats, most were short range Type IIs useful mostly for minelaying. Dönitz estimated he needed 100 boats on patrol (meaning 300 total) to win the battle. That number as not achieved until August 1942.

While almost 200 Type IX were built, when Germany declared war on the US in Dec 1941 there were only 20 operational and only 5 devoted to the initial attack on the US east coast. Germany declared war on an enemy they could barely reach, yet the US was so unprepared they did outsized damage.

  • 1
    the US entered the war in January 1942: Hitler declared war on the US on 11 December 1941
    – sds
    Dec 20, 2021 at 19:28
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    @sds Yes, I meant that as when U-Boats showed up on the US coast. I'll make it clear.
    – Schwern
    Dec 20, 2021 at 20:09
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    Snorkel XXIs with run-diesel thru periscope capability. Not used in combat however. Re. shortages: as with most things Nazi, it was an endless battle between services on resource allocation and prestige, and within the Kriegsmarine on surface fleet vs. U boats. Had the whole Tirpitz-Scharnhost-Bismarck efforts been allocated to Uboats instead pre-war, things might have looked different thru 1942 when UK-bound tonnage was being sunk fastest. Dec 21, 2021 at 1:11
  • @ItalianPhilosophers4Monica Nazi wunder weapons: always too little, always too late. Even retrofitting Type VIIs and IX with snorkels came too late to make a difference. The German battleships make more sense when you realize they were designed to fight the French, a war with Britain was not planned until years later. Their cancellation would have consequences for the disposition of the Royal Navy; more heavy units to the Mediterranean and Pacific in 1940 and 1941 possibly changing those theaters. A complex counter-factual.
    – Schwern
    Dec 21, 2021 at 2:14
  • @Schwern Oh, I don't disagree on the wonder weapons but the battleship fleet was a useless drain on Germany. Robert Forczyk, in his book Case Red, argues that the cost of battleships, far more than the Maginot Line, was what hamstrung French efforts to counter Germany. These boats were extremely costly but ended up being used very little in what was primarily a land-based context between the 2. Very little => not at all in the case of the French. Senior admirals were all about battleships, had all the procurement power and navies were senior service branches (compared to planes/sub/tanks). Dec 21, 2021 at 5:57

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