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.