From: Dictionary of American Naval Fighting Ships, Vol. IV p 165
The chief island in the northern Philippines
The first Luzon (PG-47) was laid down 20 November 1926 by Kiangnan Dock & Engineering Works, Shanghai, China ; launched 12 September 1927 ; sponsored by Miss Mary C. Carter ; and commissioned 1 June 1928.
One of eight gunboats built for service on the Yangtze River in China, Luzon was redesignated PR--7 on 15 June. From commissioning until December 1938, she served as the flagship of the Yangtze River Patrol, operating out of Hankow, between such ports as Nanking, Chunkiang, and Shanghai. In August 1937, after the Japanese had attacked Shanghai, Luzon evacuated the American Embassy staff to Chunking.
In December 1938 the river gunboat arrived at Shanghai to relieve Augusta (CA--31) as station ship. She remained off Shanghai until 29 November 1941 when she departed for the Philippines.
Luzon arrived at Manila 30 December, just 23 short, trying days after the Japanese attack on Pearl Harbor brought the United States pellmell into World War II. She then began patrol operations in the waters of the Philippines, assisting the heroic but unsuccessful defense of both Bataan, from 1 February until the surrender of the peninsula to the Japanese 9 April, and Corregidor, from the beginning evacuations of that entrance island to Manila Bay until the enemy landings 5 May.
The next day, with the surrender of the Corregidor and Manila Bay forts to the Japanese, Luzon, along with Oahu (PR--6) and Quail (AM--is), was scuttled in Manila Bay to prevent capture. But, at the same time, the strategic Battle of Coral Sea, 4 to 8 May, was in progress. The end result was an American victory: the uninterrupted Japanese push to the southeast was finally halted.
Struck from the Navy list 8 May, Luzon was salvaged by the Japanese and renamed Karatsu. For the next 2 years she operated in enemy hands until the river gunboat was sunk in the Philippines by Narwhal (SS--167) 3 March 1944.
Luzon received one battle star for World War II service.