The purpose was to obtain control of local air strips, which could be used as forward bases by fighter aircraft for operations further south.

The invasion force was supported by a flotilla of the Imperial Japanese Navy led by Vice Admiral Shoji Nishimura, consisting of the light cruiser Naka, the destroyers Murasame, Yūdachi, Harusame, Samidare, Asagumo, Minegumo, Natsugumo, six minesweepers, nine anti-submarine craft and six transports[2] The fleet deployed from Mako in the Pescadores and arrived at Vigan before dawn on 10 December.

The landing operation was covered by aircraft of the IJAAF 24th and 50th Fighter Regiments launched from the airfield at Batan Island captured the day before.

[1] At the same time as the landing operation at Aparri, the Kanno Detachment disembarked at Vigan faced no opposition from American forces; however, reports of the landing was conveyed to General MacArthur’s headquarters in Manila by a reconnaissance Curtiss P-40 Warhawk, and the Far East Air Force launched a response consisting of five Boeing B-17 Flying Fortresses and escorting P-40 and Seversky P-35 fighters of the 34th Pursuit Squadron.

A small detachment was quickly sent north to capture Laoag, capital of Ilocos Norte Province, fifty miles away, along with its airfield.