Tokyo Express
The effectiveness of PT boats in the Solomon Islands campaign, where there were numerous engagements between PTs and capital ships, as well as against Japanese shipborne resupply efforts dubbed "The Tokyo Express" operating in New Georgia Sound (called "the Slot" by the Americans), was substantially undermined by defective Mark 8 torpedoes. The Japanese were initially cautious when operating their capital ships in areas known to have PT boats, knowing how dangerous their own Type 93 torpedoes were, and assumed the Americans had equally lethal weapons. The PT boats at Guadalcanal were given credit for several sinkings and successes against the vaunted Tokyo Express. In several engagements, the mere presence of PTs was sufficient to disrupt heavily escorted Japanese resupply activities at Guadalcanal. Afterwards, the PT mission in the Solomon Islands was deemed a success.