It doesn't. "They wear war"
Imagine all of the soldiers going about putting on their armament... wearing it, in preparation for battle.
There's no direct English translation for this.
I've read some bible verses where they "girded themselves" for war, or other things. That would be the closest I've seen.
Other people wage war (Bella gerant alii), but you, get married, happy Austria.
Motto for the political alliances through marriages of the Habsbourg royal family.