U. S. TROOPS arriving in Belfast, Northern Ireland. The first U. S. troops to cross the Atlantic after the declaration of war by the United States went to Northern Ireland in January 1942. In the same month the Special Observer Group was replaced by Headquarters, United States Armed Forces in the British Isles. Shortly thereafter the center of concentration was transferred from Ireland to England and the rapid build-up of personnel commenced. Logistical planning began in April 1942. This build-up of men and supplies was to become one of the greatest logistical undertakings in military history. Supplies were shipped from the United States in ever increasing quantities until, during the month of June 1944, approximately 1,000,000 long tons were received in the United Kingdom.] [Illustration: NORTHERN IRELAND U. S. TROOPS marching through the streets of a town in Northern Ireland escorted by a British sergeant. The first U. S. troops to arrive in Ireland were 18 officers and 18 enlisted men, the advance party for the first contingent. By 1 June 1944 there were 1,562,000 U. S. troops in the United Kingdom. During the early months after the United States’ entry into World War II a large part of the equipment was similar to that of World War I. In the succeeding months much was done to improve all types of equipment and many of the changes may be seen in the pictures that follow in this volume.] [Illustration: NORTHERN IRELAND TRAINING IN IRELAND, FEBRUARY 1942. Before leaving the United States members of the U. S. armed forces normally had completed their training, but to keep the men at the peak of their fighting fitness programs in firing, field exercises, and special problems were begun under varying weather and terrain conditions. Men in their late teens or early twenties made the finest soldiers as they had stamina and recuperative power far beyond that of older men. This physical superiority often determined the issue in heavy and prolonged fighting.] [Illustration] [Illustration: ENGLAND INFANTRY MAN WITH WEAPONS. Soldier is holding a .45-caliber Thompson submachine gun M 1928A 1; from left to right are: 60-mm. mortar M 2, British antitank gun, .30-caliber U. S. rifle M 1 with bayonet M 1 attached, .30-caliber Browning machine gun M 1919A 4, hand grenades, .45-caliber automatic pistol M 1911A 1, .30-caliber U. S. rifle M 1903 with grenade launcher M 1 attached, .30-caliber Browning automatic rifle M 1913A 2, and 81-mm. mortar M 1 (top). Infantryman has just completed an obstacle course (bottom).] [Illustration] [Illustration: SCOTLAND