First blood was drawn on Christmas Eve. Ensign Robert F. Lynch celebrated the holiday by taking out the PT 122 for a routine patrol, looking for small Japanese coasters or submarines running supplies and reinforcements into Buna. The night was dark and rainy, and the PT chugged along without much hope of finding any action. PTs had no radar in those days, and a visual lookout was not very effective in a New Guinea downpour.
Even in New Guinea, however, the rain cannot go on forever. When the rain clouds parted, a bright moon lit up the sea and a lookout snapped to attention.
“Submarine,” he hissed. “Dead ahead, a submarine.”
Hove to on the surface was a Japanese I-boat, probably waiting for Japanese small craft to come from the beach for supplies, or else recharging its batteries, or probably both. Ensign Lynch began his silent stalk and closed to 1,000 yards without alarming the submarine’s crew. He fired two torpedoes and kept on closing the range to 500 yards, where he fired two more. The submarine went up in a geyser of water, scrap iron, and flame.
Ensign Lynch thought he saw a dim shape beyond his victim and was alert when another surfaced I-boat shot four torpedoes at him. He slipped between the torpedo tracks, but could do nothing about retaliating, because he had emptied his tubes. He had to let the second I-boat go. Postwar assessment gives Ensign Lynch a definite kill on this submarine.
The same Christmas Eve, two other PTs from the Oro Bay base sank two barges full of troops.
Ensign Lynch’s torpedoing of the submarine—the first combat victory of the PT fleet in New Guinea waters—was a spectacular triumph, but the sinking of two barges was much more typical of the action to come.
The terrible attrition of ships in the Guadalcanal fight had left the Japanese short of sea transport. Besides, Allied airmen made the sea approaches to New Guinea a dangerous place for surface craft in daylight. Nevertheless, the Japanese had to find some way to supply their New Guinea beachheads by sea or give them up, so they began a crash program of barge construction.
The barges were of many types, but the most formidable was the daihatsu, a steel or wooden barge, diesel powered, armored, heavily armed with machine guns or even with automatic light cannon. They could not be torpedoed, because their draft was so shallow that a torpedo would pass harmlessly under their hulls. They could soak up enormous amounts of machine-gun fire and could strike back with their own automatic weapons and the weapons of soldier passengers. A single daihatsu could be a dangerous target for a PT. A fleet of daihatsus, giving each other mutual fire support, could well be too much to handle even for a brace of coordinated PTs.
The naval war around New Guinea became a nightly brawl between daihatsu and PT, and the torpedo function of the PT shriveled. Eventually many of the boats abandoned their torpedo tubes entirely and placed them with 37-mm. and 40-mm. cannon and extra 50-caliber machine guns, fine weapons for punching through a daihatsu’s armor. The PT in New Guinea gradually changed its main armament from the torpedo—a sledge-hammer type of weapon for battering heavy warships—to the multiple autocannon—a buzz-saw type of weapon for slicing up small craft.