http://www.globalfirepower.com/The site is a joke, does not take technology into account. Technology is the game changer. Superior technology is what allowed Nazi Germany to romp through Europe in 1939-1943 with such ease. Russian industrialization and imports of American made planes is what allowed them to survive and repel Germany.
Iraq had the 3rd largest army in the world pre Kuwait war (1991), yet its army was torn to shreds by America's superior firepower (technology), it wasn't even a war it was an international execution.
As it currently stands Canada does not have the technology invested to fight a war, 15th place in the world is very generous.
ps. The NATO military alliance requires all members to be at war with an aggressor nation if that nation attacks a member.