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On January 12, 1942, the USS Trout (SS-202) sailed from Pearl Harbor captained by Lieutenant Commander Frank W. "Mike" Fenno, Jr., on a special mission to bring supplies to American forces under siege by the Japanese on Corregidor Island. The submarine had been stripped of most bulky items except for one torpedo in each of its tubes in order to accommodate 3,500 rounds of high altitude three-inch antiaircraft ammunition. On February 3, 1942, at 1830 hours, the Trout effected a rendezvous with the motor torpedo boat PT-43 off Corregidor and was escorted around the north side of the island to the wharf on the south side of the fortress. There she offloaded the antiaircraft ammunition. She then took on fuel and two torpedoes. To compensate for the ballast lost from the weight of the antiaircraft ammunition, the Trout embarked twenty tons of cargo consisting of gold and silver bars; securities belonging to the Philippine Commonwealth, banks, mines, and residents of the islands; and regular mail and secret U. S. State Department mail. This valuable cargo was to be taken to Pearl Harbor and thence shipped to Washington, D.C. for safekeeping. At 0400 hours, the Trout cleared the dock and rested on the bottom of Manila Bay until the following night. When she surfaced more mail and securities were shuttled to her by a launch. Overall the cargo had an estimated value of $10 million. The Trout was then escorted clear of a minefield by the torpedo boat and entered the open sea. Fenno conned Trout for her assigned patrol area in the Bonin Islands.

On February 10, 1942, at 1700 hours, Fenno made a submerged sonar attack on the 2,719-ton Japanese cargo vessel Chuwa Maru. The Trout fired three torpedoes. Two of them hit the Chuwa Maru and she sank. Five hours later, Fenno conducted a submerged periscope attack on the 6,788-ton Japanese cargo vessel Kurama Maru. One of the three torpedoes Fenno fired hit the vessel and she probably sank. 1

Around this time the Japanese Navy had begun to mobilize and arm hundreds of fishing boats and other small commercial vessels to serve as converted gunboats, mine sweepers, patrol boats, submarine chasers, and miscellaneous "auxiliaries." They were manned by their civilian crews with Japanese naval officers in command. Those that had sails also had engines. According to Commander John D. Alden, USN (ret.), the vessels were referred to as tokusetsu kanshitei or specially equipped guard boats. They were armed with light deck guns, machine guns, handguns, and depth charges. They were also equipped with powerful radio transmitters. Thus when used as picket boats in outlying areas they could relay warnings about the presence of enemy forces. Their displacements fell mostly between 150 and 250 tons. At this point in the war American submarine skippers knew little about the tokusetsu kanshitei. Mike Fenno was about to make the first recorded attack by an American submarine on one of them. On February 20, 1942, Fenno made a night surface attack on what he described as an unknown type of patrol vessel. He fired three torpedoes at it and claimed one hit. Back at Pearl he was credited with sinking a 200-ton patrol craft. 2

The proliferation of these small picket boats would soon influence American submarine policy on surface gun actions. The use of torpedoes against these agile small targets was neither productive or cost effective. The use of surface gun actions as a tactic to destroy them became more common as the war progressed. The number of submarines making gun attacks on enemy vessels increased at a compound annual growth rate of 52.11 percent from 1942 through 1945. There was also a corresponding increase in the number, size, type, and power of guns installed on each submarine. 3

Mike Fenno was awarded the Army's Distinguished Service Cross and the Navy Cross for this special mission to Corregidor; each of the Trout’s seventy officers and enlisted men were awarded the Silver Star.

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1. Alden, John D., Commander, USN (ret.) and Craig R. McDonald, United States and Allied Submarine Successes in the Pacific and Far East During World War II, Fourth Edition, see USS Trout (SS-202), Attack Nos. 61 and 62.

2. Alden, John D., Commander, USN (ret.), "Those Pesky, Plucky, Picket Boats, Part I," The Submarine Review, April 2011, p. 91-93; Submarine war patrol reports on CD, USS Trout (SS-202), data collected by the Submarine Operations Research Group (SORG) in the report "U. S. Submarine Attacks Listed by Date and Hour of Attack."

3.  Sturma, Michael, Surface and Destroy: The Submarine Gun War in the Pacific, p. 179-180.