PT Boat - Service

Service

Originally conceived as anti-ship weapons, PT boats were publicly credited with sinking several Japanese warships during the period between December 1941 and the fall of the Philippines in May 1942. Attacking at night, PT crews may have sometimes failed to note a possible torpedo failure. Although the American Mark 8 torpedo did have problems with porpoising and circular runs, it could and did have success against common classes of targets. The Mark 3 and Mark 4 exploders were not subject to the same problems as the Mark 6 exploders on U.S. submarines' Mark 14 torpedoes. Introduction of the Mark 13 torpedo to PT boats in mid-1943 all but eliminated the early problems that PT boats had with their obsolete Mark 8s.

PTs would usually attack under the cover of night. The cockpits of PT boats were protected against small arms fire and splinters by armor plate. Direct hits from Japanese guns could and did result in catastrophic gasoline explosions with near-total crew loss. They feared attack by Japanese seaplanes, which were hard to detect even with radar, but which could easily spot the phosphorescent wake left by PT propellers. Bombing attacks killed and wounded crews even with near misses. There are several recorded instances of PT boats trading fire with friendly aircraft, a situation also familiar to U.S. submariners. Several PT boats were lost due to "friendly fire" from both Allied aircraft and destroyers.

Initially, only a few boats were issued primitive radar sets. Later in the war, as more PTs were fitted with dependable radar, they developed superior night-fighting tactics and used them to locate and destroy many enemy targets. During the Guadalcanal and Solomon Island campaigns in 1942–1943, the PT boats of Squadron (RON) 2, 3, 5 and 6 would lie in wait to ambush a target from torpedo range (generally about 1,000 yards (910 m)). During some of these nighttime attacks, the PT boats' position may have been given away by a flash of light caused by grease inside the black-powder-actuated Mark XIII torpedo tubes catching fire during the launching sequence. In order to avoid return fire by the enemy ships, the PT boat could deploy a smoke screen using stern-mounted generators as they escaped and evaded the enemy ships. The enemy forces would use searchlights or seaplane-dropped flares to locate the fleeing PT boat, illuminating them for destruction by their heavy-caliber guns. Sometimes PT boats used depth charges as a last-ditch confusion weapon to scare off pursuing destroyers. They could adjust the depth charge setting to go off at 100 feet (30 m), and by the time it exploded the pursuing destroyer would be right above the explosion. Starting in mid-1943 and thereafter, the old black powder actuated Mk13 Torpedo tubes loaded with Mark 8 torpedoes were removed and replaced with a newer style of torpedo launcher. The new Mark 1 "Roll-off" Torpedo launcher rack (which was loaded with an improved Mark 13 aerial torpedo) effectively eliminated the problem of a flash of light giving away the position of the PT boat as a result of burning grease. The new launcher did not use any form of explosive to launch the torpedo, and it was about 1,000 pounds (450 kg) less weight than the old tube style launchers.

During the war, a few PT boats were modified to become a "PT Gunboat". In the PT Gunboat, the torpedoes were all removed and replaced with more and heavier guns. These versions mounted extra armor, though tests showed this was not very effective.

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" in "the Slot", 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, since they knew how dangerous their own Type 93s 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.

Throughout World War II, PTs operated in the southern, western, and northern Pacific, as well as in the Mediterranean Sea and the English Channel. Some served during the Battle of Normandy. During the D-Day invasion, PTs patrolled the "Mason Line", forming a barrier against the German S-boats attacking the Allied landing forces. They also performed lifesaving and anti-shipping mine destruction missions during the invasion.

Perhaps the most effective use of PTs was as "barge busters". Since both the Japanese in the New Guinea area and the Germans in the Mediterranean had lost numerous resupply vessels to Allied air power during daylight hours, each attempted to resupply their troop concentrations by using shallow draft barges at night in very shallow waters. The shallow depth meant Allied destroyers were unable to follow them due to the risk of running aground and the barges could be protected by an umbrella of shore batteries. PTs had sufficiently shallow draft to follow them inshore and sink them. The efficiency of the PT boats at sinking the Japanese supply barges was considered a key reason why 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 ten feet (3 m) and the barges only drew five (1.5 m). To accomplish the task, PTs in the Mediterranean and the Pacific (and RN and RCN MTBs in the Med) installed more and heavier guns which were able to sink the barges. One captured Japanese soldier's diary described their fear of PT boats by describing them as "the monster that roars, flaps it wings, and shoots torpedoes in all directions."

Though their primary mission continued to be attack on surface ships and craft, PT boats were also used effectively to lay mines and smoke screens, coordinate in air-sea rescue operations, rescue shipwreck survivors, destroy Japanese suicide boats, destroy floating mines, and to carry out intelligence or raider operations.

After the war, American military interviews with captured veterans of the Imperial Japanese Navy, supplemented by the available partial Japanese war records, were unable to verify that all the PT boat sinking claims were valid. Like many other victory claims by all parties involved (aircraft pilots, surface ships, submarines) this unclear verification was due in part to the Japanese military's policies of destroying military records.