Naval Historywith Dr. Alex

Q&A · 3:32:51-3:35:55

If the United States built ten 8-inch-gun submarines

A pre-1930 American program would reshape treaty allowances, but wartime navies would likely remove the guns and exploit the large hulls for range, torpedoes, or aircraft.

Alternate HistoryCruiser SubmarinesFirst London Naval Treaty (1930)Imperial Japanese NavyM Class SubmarinesSurcouf (Submarine)T Class Submarines
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Question

How would ten American submarines armed with 8-inch guns be used in World War II?

Short answer

The preferred use is to remove the heavy guns and exploit the large hulls for long-range patrols or torpedo batteries. Japanese responses could instead favour guns or aircraft.

Notes

An American order prompted by Surcouf and placed before the 1930 London Naval Treaty could force negotiators to accommodate ten large gun submarines. Britain might seek an equal allowance, with other powers receiving proportional numbers. By World War II, removing the 8-inch guns could leave useful large hulls for long-range patrols. British experience with M1, M2 and M3 gives a reason to abandon the heavy-gun concept and build something closer to an enlarged T class, perhaps firing about twelve torpedoes forward. Two Japanese responses are suggested: more guns for night attacks, or earlier development of aircraft-carrying submarines resembling the I-400 concept. A decade of construction and doctrinal development would separate the original congressional decision from the boats' eventual wartime role.