When did American Soldiers come to Britain in world war 2?

The first few divisions arrived in the UK by late spring of 1942. They continued to arrive steadily, reaching a peak just before the Normandy landings of June 1944. A few more divisions passed through the UK after the D-Day landings, arriving from the states and transhipping on to the continent. In addition to the several million ground troops, about two million men served in the 8th US Air Force, based in the UK and engaged in the daylight strategic bombing of Europe. The 9th US Air Force was also based in the UK, with the mission of providing tactical support to troops on the ground. Many 9th AF personnel and units moved to the continent once airfields became available there, but the 8th AF was based in the UK throughout.