On 22 December, a Japanese convoy left Miri for Kuching, but was spotted by the Dutch flying boat "X-35", which radioed a warning to the Dutch submarine , under the command of Lieutenant Commander Carel A. J. van Groeneveld. At 20:40 on 23 December, "K XIV" infiltrated the convoy and began its attack. The army transports "Hiyoshi Maru" and "Katori Maru" were sunk with the loss of hundreds of troops. was beached to prevent her from sinking, and another transport was less seriously damaged. The rest of the troops were able to land. Although 2nd Battalion, 15th Punjab Regiment, resisted the attack, they were soon outnumbered and retreated up the river. By the afternoon, Kuching was in Japanese hands.