The efficiency of the PT boats at sinking the Japanese supply barges was considered a key reason that the Japanese had severe food, ammunition, and replacement problems during the New Guinea and Solomon Island campaigns, and made the PT boats prime targets for enemy aircraft. The use of PT boat torpedoes was ineffective against these sometimes heavily armed barges, since the minimum depth setting of the torpedo was about 10 feet (3 m) and the barges drew only 5 feet (1.5 m).