Complex sentence: With the end of hostilities in September 1945, the training B-29 aircrew training program began to scale down and the base became a reception facility for returning Twentieth Air Force bomb groups from the Marianas.
Split into simpler sentences: With the end of hostilities in September 1945 the training B-29 aircrew training program began to slow down. The base became a reception facility for returning Twentieth Air Force groups from the Marianas.