Chief Arnook: "Those Fire Nation Bastards are coming, send out the army."
Advisor: "What army?"
Chief Arnook: "Oh yeah..."
— Yep, they don't have an army

Every nation in the avatar world has some army or navy or whatever, even those stupid hippies have atleast weapons. The losers losers at the poles, Canada, and the swamp don't, not even a stick. Yeah, the got a couple nooobs to dress up in some fancy costumes and crap, but seriously they don't. Because they are in a polar area, not a lot of people wanna rule there so they never needed one. However, one day the Fire Nation attacked the Southern Water Tribe, and they killed everyone important but Katara. Those Sexist Bastards in the north had some icebergs and polar bears to protect them. But because of global warming, the polar bears died out. So, the Fire Nation came in and would have kicked their butt, if it wasn't for the avatar, a cat fish spirit, and the PWNage state the avatar state they would have all died up there.