The 545th Bombardment Squadron (Heavy) was activated on 1 December 1942, at Gowen Field, Idaho, as a unit of the 384th Bombardment Group (Heavy). It was placed under the command of 1st Lt Raymond P Ketelsen and commenced training at Wendover, Utah, on 2 January 1943, continuing there until 1 April 1943. The unit then moved to Sioux City, Iowa, for final training.
The Group received orders in late April to move to their combat assignment in England. Squadron aircrews left Sioux City with their new B-17Fs for Kearney, Nebraska on 3 May 1943, and then continued to Prestwick, Scotland via Presque Isle, Maine, and Goose Bay, Labrador; one contingent was routed via Gander, Newfoundland instead of Goose Bay. The ground unit left for Camp Kilmer, New Jersey on 9 May 1943, sailing on the Queen Elizabeth on 27 May 1943, and arrived in Greenock, Scotland on 2 June 1943.
On arrival in England, the 545th established its home at Grafton Underwood Airfield, Station 106, Northamptonshire. Combat training continued through June, and the Squadron flew its first operational mission on 22 June 1943, with seven Squadron aircraft taking part. Combat losses were a fact of life from the very first mission, with one Squadron aircraft lost to enemy action with the Olbinski Crew. Of the ten-man crew, six were captured and became POW for the rest of the war; the other four died in the event.
Between 22 June 1943, and 25 April 1945, the 545th crews flew 2,475 sorties, against targets in Germany, France, Poland, Belgium, Czechoslovakia, and Holland. The Squadron lost 60 B-17s and 380 men, of whom 127 were KIA, 15 were MIA, 209 were POW, 13 evaded, and 5 were interned in neutral countries: another 11 men were lost to other causes.
First Lieutenant (later Major) Raymond P Ketelsen - 28 December 1942 to 27 April 1944
Captain Robert E Langlois (Acting) - 9 April 1944 to 24 April 1944 (lost on combat mission)
Lieutenant Colonel Oattis E Parks - 27 April 1944 to 29 August 1944
Captain (later Major) Arthur M Stone, Jr - 31 August 1944 to 10 January 1945 (lost on combat mission)
Major (later Lieutenant Colonel) Alexander C Strickland - 15 January 1945 through the Istres period