Ancestry.co.uk had two records of men in 1917 with the surname McIlhaga, first Robert an Able Seaman and 'J' a Soldier. Robert was in a Crew List on the ship RMS Niagara leaving Vancouver and arriving Honolulu, Hawaii on 13 June 1917. He had in fact been engaged at Sydney, New South Wales, on 10th May. Robert's surname was really McIlhagga and I wrote about him on 14th July 2009 when I mentioned the ship Niagara. He eventually made Sydney his married home ten years later. He must have liked what he saw in 1917.
'J' McIlhaga was 435607 Private McIlhaga of 22nd Battalion, D Company (Canadian Infantry?), also on a ship, Essequibo, being transferred from engagement in the First World War to Canada, presumably his home. The only 'J' who fits other information I have was Joseph McKee McIlhagga who ten years later was to marry Catherine Walker Ross. In 1917 Joseph would have been 25. My notes on him say he attained the rank of Colour Sergeant, though that may have been a temporary 'Acting' rank.
The 1917 information I have comes from a Nominal Roll of NCOs and men who embarked at Liverpool on 19th February for Canada. The list makes very sad reading for the 41 men listed were suffering from a range of injuries from amputations and shrapnel wounds to shell shock. Several injuries were marked 'Mental', including that of J. McIlhaga who had been diagnosed with Neurasthenia, a term used to indicate the exhaustion of the central nervous system's energy reserves, exactly what one would expect of someone who had had to face the horrors of trench warfare in France. Incidentally, 'J''s name, if he were Joseph, was also McIlhagga.