But this is the Broken Window Fallacy. There is no net economic benefit to us in manufacturing arms and blowing stuff up. If there were, we wouldn't need a foreign war to achieve it.

There's a target range for anti-tank missiles just south of my office. About a mile and a half away - from the firing line they could definitely hit my office if they were sufficiently careless. They could pick up the pace in peacetime and fire hundreds of missiles every day if such a thing provided an economic benefit.