Complex sentence: He took part in the invasion of Normandy in 1944, with the 2nd Battalion and was a member of the first British unit to enter Brussels, and later was appointed Military Assistant to Harold Macmillan, then the Resident Minister in North Africa.
Split into simpler sentences: He took part in the invasion of Normandy in 1944 with the 2nd Battalion and was a member of the first British unit to enter Brussels. He was later appointed Military Assistant to Harold Macmillan, then the Resident Minister in North Africa.