Final answer:
Arthur Harris did not join US bombings because he was tasked with leading the British bombing strategy, which was to carry out night area bombings of German cities as part of a coordinated Allied effort with the U.S., who conducted precision day bombings.
Step-by-step explanation:
Arthur Harris, commonly known as "Bomber Harris," was the Air Officer Commanding-in-Chief of RAF Bomber Command during the latter half of World War II. The primary strategy devised by the Allied forces, as agreed upon by Churchill and Roosevelt at Casablanca, was to bomb German cities with the aim of hindering Germany's war-making capacity by targeting factories and transportation lines. The United States would precision bomb industrial and military targets during the day, while the British would area bomb cities by night.
The decision-making process did not directly involve Harris joining American bomber crews or acting under U.S. orders. Instead, his role was to carry out the British part of the strategy. The strategic bombing led by Harris was pivotal to Allied efforts in Europe but distinctly separate from that of the U.S. bombings. The combined effort of day and night bombings by the U.S. and Britain was designed to maximize the impact of Allied air power against Nazi Germany.