I have found records for two Hillmans who served in the First World War. Their attestation papers can be found at http://www.collectionscanada.gc.ca
The first is Daniel Hillman(Nov.6, 1877-1975). He was the son of William James Hillman and Margaret(Patterson) Hillman. He joined the Canadian Corps March 1915 in Montreal with the rank of Lieutenant. He was a civil engineer who specialized in railroad construction. On the Western Front he worked with the railroad engineers constructing narrow gauge track to the front lines. He came out of the war with the rank of Lt. Colonel.
The second is John Alexander William Hillman(21 Nov.1893-?). He was the son of Neil Hillman and Elizabeth(Chisholm) Hillman. He joined the Canadian Corps Jan. 5, 1918 in Brantford, Ontario. He joined with the rank of Corporal. I am still researching to find his unit and thus where he served in the last year of the war.
One thing that strikes home as you read their attestation papers is the size of both men. They are both 5’4” tall. Interesting as most of the male Hillmans I know now are 6 footers.