Patrick Deegan, who is 29, admitted in January to uttering death threats and to illegally possessing a firearm.
He emailed the threat to the Calgary fire department last May.
The judge said Deegan had an unhealthy obsession with war and his threat had to be taken seriously.
Deegan is getting credit for time already served, but still faces almost 16 months behind bars.
He read a tearful apology to the court in which he said he had breached the trust of his family and the public.