Complex sentence: He was appointed Director of Plans at the Headquarters of the Supreme Allied Commander South East Asia in February 1944 and became a wing commander on a temporary basis on 1 July 1944 and on a war substantive basis on 11 August 1944.
Split into simpler sentences: He was appointed Director of Plans at the Headquarters of the Supreme Allied Commander South East Asia in February 1944. He became a wing commander on a temporary basis on 1 July 1944 and on a war substantive basis on 11 August 1944.