Complex sentence: He was given the brevet rank of colonel on 1 July 1935; this became temporary on 1 July 1936 and finally substantive on 1 July 1937, over twenty years after he had become a lieutenant colonel in the AIF.
Split into simpler sentences: He was given the brevet rank of colonel on 1 July 1935. It became temporary on 1 July 1936 and finally substantive on 1 July 1937, over twenty years after he had become a lieutenant colonel in the AIF.