The United States Army was well-settled in Northern Ireland by the Spring of 1942. On 10th March 1942, an Officer Messenger Service began between Wilmont House, Dunmurry, Co. Antrim and other US Army bases across Ulster.
Communication was vital to the military in wartime and the US Army had several postal units in Northern Ireland. Among them was 577th Army Postal Unit who remained in Ballymena, Co. Antrim until 10th March 1944.