Lt Fergusson was with the 15th Battalion, 48th Highlanders. At Amiens on April 30 1918, leading a defensive patrol at night, seeking German prisoners. He was wounded on August 8 while attempting to bomb an isolated post but after having his wound dressed he carried on. Later that day he took command of No. 2 Company to plug a dangerous gap between the 5th Battalion and 1st Brigade. His company then held the forward position until relieved by the 2nd Battalion on the 10th. During the assault at the Drocourt-Queant Line on 1 September he was wounded again while moving forward and passing the 16th Battalion.

When war was declared in September 1939, Lt Fergusson became one of 52 Officers  to join the 2nd Battalion and train, in preparation for overseas assignment, at the Canadian National Exhibition grounds starting that month. The training was dubbed Maybin’s Academy, after the Officer Commanding the training, Major Wm. Maybin, MC who had been commissioned in the field while with the 15th Battalion, 48th Highlanders in WWI. The 48th had set up training without waiting for orders from higher up in the army.