Stanley Allen was the son of George and Agnes Allen, of Liverpool, England; husband of Florence MacDonald Allen, of Wellington City, New Zealand.

Stanley Allen attended King's College, Auckland from 1906 to 1915. He trained at Duntroon Military College (Australia) and served in India on the north-west frontier. Returning to England he trained as a signalling officer in Yorkshire and came to New Zealand in January 1929 being appointed Area Officer at Hamilton with the rank of captain. He was a member of the First Echelon to the Middle East and Divisional Signals Officer.

He was awarded an OBE (Officer of the British Empire)

Stanley Allen commanded 21 Battalion from 7 December 1941. At the time of his death they were taking part in the Defence of Egypt. The battle was at Reweisat Ridge. An account of the fighting is recorded in the Official History which quotes from Staff-Sergeant Philip's writings:

'[Ten minutes after we started] an Italian soldier joined up with us giving us some Nestles chocolate and a cold cocoa drink [then] four more Italians thrust themselves upon us insisting on going back with us. [Shortly afterwards we heard] voices ahead [and]I investigated, taking one of our prisoners on my bayonet. We had run into a strong point overlooked in our advance and I was set upon by several Italians. I was bayonetted and shot through the knee and chin [Colonel Allen received four bullets in the chest and died about 3 p.m.]...' (p. 176) AWMM