Complex sentence: In 1936, he became an officer in the service of the Life Guards and fought in the Second World War, was afterwards invested as an Officer of the British Empire in 1945 and rose to the rank of Lieutenant-Colonel in 1946.
Split into simpler sentences: In 1936, he rose to the rank of officer in the service of the Life Guards and fought in the Second World War. He was afterwards invested as an Officer of the British Empire in 1945 and rose to Lieutenant-Colonel of the Life Guards in 1946.