Warriors of the Northern Water Tribe used an array of weapons along with vehicles such as boats to fight of invaders.

Infantry

All the tribe's men are fully trained warriors. Their army includes quite a few benders, and their medics are the healers. Their soldiers when on special missions have 3 vertical wavy lines painted on their heads when fighting.

Navy

The Northern Water Tribe uses catamaran-like boats for fishing and warfare.

Korra's Time

In Korra's time, the Northern Navy is as powerful as the Fire Nation's navy was in The Hundred Year War.

It is only featured in Season 2 of TLOK as the North Attacks the Southern Tribe, but is a very powerful sight.