Complex sentence: The Royal Auxiliary Air Force (RAuxAF) was commanded by an Air Vice-Marshal and provided reinforcements to the Royal Air Force, which were manned by civilians and called upon in times of need or war.
Split into simpler sentences: The Royal Auxiliary Air Force (RAuxAF) was commanded by Air Vice-Marshal. It provided reinforcements to Royal Air Force, which were manned by civilians and called upon in times of need or war.