Hornby enlisted in the 19th Alberta Dragoons to fight during World War I, where he met Norman Lubbock Robinson, who would later work with him in Canada's north.
[1] In 1923, Hornby teamed up with the Englishman James Charles Critchell Bullock (1898-1953) in efforts to spend an entire year in the Arctic near Hudson Bay living off the land without supplies except for weapons.
The pair barely survived and Critchell Bullock's diaries formed the basis of Malcolm Waldron's book Snow Man: John Hornby in the Barren Lands, first published in 1931.
In 1926, Hornby tried to spend a year in a spot by the Thelon River with his 18-year-old cousin Edgar Christian and another young man, Harold Adlard.
Hornby recommended in a report following his expedition with Critchell Bullock that the areas near the Thelon and Hanbury Rivers be created as a wildlife sanctuary.