Born on July 22, 1923 Alan Crabtree was the middle son of Edith and Maurice Crabtree of Toronto.
Both Alan and his brother Charles enlisted in the Royal Canadian Air Force as soon as they were able during the Second World War. Alan obtained his pilots wings at the No.2 Harvard Flight Training School in Uplands, Ottawa in January 1944. He had trained on Harvards expecting to be a fighter pilot. However once they arrived overseas, his entire graduating class was transferred to Bomber Command.
Alan served with Squadron 189, flying a Lancaster Bomber in 5 Group with Bomber Command. Alan returned home safely at the end of the war. Not long after his return to Canada Alan attended Osgoode Hall Law School and graduated in 1951. He practiced law with his late father Maurice Crabtree, M.C. K.C. who was a veteran of the First World War. Alan's brother Charles did not survive the war.