Hornbill was laid down as YMS-371 on 17 November 1942 by Weaver Shipyards, Orange, Texas and launched 27 November 1943. She was completed and commissioned on 29 February 1944, Lt. J. L. Grace in command. After her commissioning, YMS-371 participated in operations in the Gulf of Mexico until the summer of 1945, when she transited the Panama Canal en route to Okinawa, where she arrived 5 July to begin minesweeping operations. On 17 August, she departed Okinawa for Japan to sweep mines in Tokyo Bay, around the island of Honshū and in the naval base of Sasebo.