USS S-20 (SS-125)

USS S-20 (SS-125) was a first-group (S-1 or "Holland") S-class submarine of the United States Navy. Her keel was laid down on 15 August 1918 by the Bethlehem Shipbuilding Corporation in Quincy, Massachusetts. She was launched on 9 June 1920 sponsored by Miss Anne Claggett Zell, and commissioned on 22 November 1922 with Lieutenant John A. Brownell in command.

S-20 was rebuilt in 1924, with a larger bow (similar to that of the V-1 class) to improve seakeeping and blisters on the upper hull to hold more fuel, but this modification was not repeated on any other members of the class. She was also used as an experimental engine test vessel, with a new high-speed geared-drive 600 hp MAN diesel replacing her starboard engine in 1931.

In 1932, this new engine was replaced by a prototype diesel-electric plant. This was a MAN-type 635 hp 16-cylinder engine running at even higher speed, driving an electrical generator, built by General Dynamics Electric Boat and designated 16VM1. Electricity produced by the generator was used to drive a high-speed electric motor geared to the shaft; there was no direct connection between the diesel engine and the shaft. Diesel-electric propulsion was then adopted for many U.S. submarines through World War II, starting with the 1932 Porpoise class; other navies did not follow suit until after the war.

Inter-War Period
In addition to duty in northeastern points out of New London, Connecticut from 1922–1929, the new submarine visited Coco Solo in the Panama Canal Zone in March 1923; served at Saint Thomas, United States Virgin Islands in February 1924; and operated in the Panama Canal area from January through April 1926. S-20 visited Kingston, Jamaica from 20–28 March 1927, and served again in the Panama Canal area from 17 April 1929-November 1930. Departing Coco Solo on 7 November, S-20 arrived at Pearl Harbor on 7 December. Following duty there, she sailed on 20 February 1932, and from March 1932-April 1933, served at Mare Island. Later, she operated mainly at San Diego, California into 1934. Departing San Diego on 15 March, S-20 returned to New London on 28 October. From then until December 1941, she operated there as part of a test and evaluation division. During this period, she visited Guantanamo in February-March 1938; served in the Panama Canal area from January-March 1939; and visited Guantanamo again in February 1940. Her commanding officer in 1936-1937 was Lieutenant John P. Cromwell, a future posthumous Medal of Honor recipient for his actions aboard USS Sculpin (SS-191) in 1943.

World War II
From December 1941-July 1945, S-20 continued to operate from New London. Her operations were off New England and often included training activities at Casco Bay, Maine. Departing New London on 2 July 1945, S-20 was decommissioned on 16 July at Philadelphia, Pennsylvania. Her name was struck from the Naval Vessel Register on 25 July. She was sold on 22 January 1946 to North American Smelting Company, Philadelphia for scrapping.