Qualla: Japanese submarine Ro-100

Japanese submarine Ro-100: Introduction

Thu, 16 Apr 2026 00:00:00 GMT

Her own seaplane bombed her first. On 6 February 1943, just days after setting out from Truk toward Rabaul, Ro-100 was transiting the Bismarck Sea on the surface when an Aichi E13A floatplane - Allied codename "Jake," and supposedly on her side - mistook her for an enemy vessel and attacked. She survived with minor damage. It was the beginning of one of the unluckiest service careers in the Imperial Japanese Navy's submarine fleet. In the twenty-two months that followed, Ro-100 would be rammed by depth charges, holed on a reef, missed by four torpedoes from an unidentified submarine, strafed by an Allied patrol plane, and - finally, in November 1943 - blown open by a naval mine while running supplies to starving Japanese soldiers on Bougainville.

Japanese submarine Ro-100: A Coastal Boat

Thu, 16 Apr 2026 00:00:00 GMT

Ro-100 was not one of the big Japanese fleet submarines designed to cross oceans and attack American battle lines. She was a coastal type, sixty meters long, with a crew of fifty, derived from the earlier Kaichu class. On the surface she could manage about 14 knots; submerged, 8....

Japanese submarine Ro-100: The Destroyer and the Crewman

Thu, 16 Apr 2026 00:00:00 GMT

Her first real test came on 14 February 1943, off Port Moresby. Ro-100 sighted an Allied convoy and began a submerged approach. Her commanding officer, concentrating on the target, neglected the standard periscope sweep and did not see the Allied destroyer bearing down on him. Th...

Japanese submarine Ro-100: Patrols That Found Nothing

Thu, 16 Apr 2026 00:00:00 GMT

Through the summer of 1943, Ro-100 was assigned patrol area after patrol area southeast of Guadalcanal, north of New Guinea, south of Rendova. Most of these patrols were uneventful. The Allies' convoys had learned to stay elsewhere; the submarines that did sight them were often t...

Japanese submarine Ro-100: The Last Run

Thu, 16 Apr 2026 00:00:00 GMT

On 1 November 1943, U.S. Marines landed at Cape Torokina and the Bougainville campaign began. Japanese forces on the island were cut off from easy resupply by sea. The garrisons at Buin and elsewhere needed food, and submarines like Ro-100 were among the few assets that could sti...

Japanese submarine Ro-100: The Swim to Buin

Thu, 16 Apr 2026 00:00:00 GMT

Fifty men had sailed on Ro-100. Twelve came home. Survivors in the water began swimming toward the lights of Buin, a few miles to the north. Sharks found them first. The accounts are stark: men who had survived the first explosion, who had gotten out of a sinking submarine in the...