Battle flags in World War II kept an unofficial record of the number of ships a submarine sank. Warships were represented by the rising sun version of the Japanese flag, while the merchant vessels were represented by the "meatball" flags. The submarine's logo was also featured on the flag. The difficulties in assessing actual damage from attacks on the enemy led many submarines to overestimate their successes. After the war, an Allied naval review board discovered inaccuracies as great as thirty percent during an examination of Japanese losses credited to American submarines.
During World War II, USS Flying Fish patrolled the waters off of Midway, Taiwan, Iwo Jima and the Marianas Islands. While under the command of Commander Robert D. Risser, and Lieutenant Commander Julian T. Burke, Flying Fish received 12 battle stars and was credited with damaging a Japanese battleship. She was also one of the first boats to be outfitted with mine detection gear for use in the Sea of Japan. The flag shows that Flying Fish had sunk six warships and 13 merchant vessels in its 12 war patrols by late May 1945.
From 25 July 1943 to 27 August 1945, USS Balao served in the Pacific Ocean. Her flag shows that Balao destroyed one warship and nine merchant vessels during her ten patrol. Postwar assessments, however, reduced the claim to seven Japanese ships totaling 36,500 tons plus an additional 1,100 tons of enemy small craft. For her services in World War II, Balao received nine battle stars. Balao's flag was designed by a Disney artist at the request of Motor Machinist's Mate 3rd class William G. Hartley in 1945.
Commissioned on 19 May 1944, USS Spot registered the destruction of 16 merchant vessels on her three war patrols in the Pacific. Much more elaborate than the other flags, Spot's flag not only records the number of kills, but also lists the ships' names. As seen on the flag, Spot successfully shelled the radio station at Kokuzan and disabled the passenger freighter Foochow. She received four battle stars for her services in World War II.
Launched 1 June 1942, Gurnard first patrolled the Bay of Biscay for German blockade runners. By 12 June 1943, she was transferred to the Pacific Ocean. There, Gurnard received six battle stars and the Navy Unit Commendation, while her captain, Lieutenant Commander C.H. Andrews, earned the Navy Cross. Gurnard had one of the highest single patrol tonnage scores during World War II -- 29,700 tons. Her battle flag shows that she destroyed 12 combatant and merchant vessels. The flag also records the total tonnage of the ships sunk. However, postwar study proved that Gurnard succeeded in sinking only 10 ships -- 57,866 tons.