After returning to civilian life, he was Director-General of the Royal United Services Institute for Defence Studies.
[1] In 1942, Younger took part in trials on the Scottish island of Gruinard to test the potential of anthrax as a weapon.
[5] In 1943, Younger was given command of 26 Assault Squadron, a unit with bridge-laying and other specialist tasks, with instructions to prepare to lead the 7th Brigade ashore on D-Day.
[6] He had a large part in modifying the Royal Engineers Assault Vehicle, or AVRE, into a suitable landing craft, and practiced by invading the Isle of Wight.
[6] Coming ashore near Courseulles, he was wounded and lost the hearing in one ear, so was returned to Portsmouth, but was flown back into the action in time to assist with the crossing of the Rhine.
[6] Younger took part in the Korean War between 1950 and 1951, being given command of 55 Field Squadron, Royal Engineers.