For Trump, who wants to "bring back jobs," it absolutely could be a way to increase jobs where he take total credit for it. It's not a GOOD method, because of the cost, obviously (financial and human). But, he doesn't care; he's kowtowing to the Republicans and his base.
It's a pretty common capitalist economic belief that war "creates jobs." As does increased defense. As
@
Dra508
said, from a government spending and job-creation standpoint, defense is no different than infrastructure.
Anyway, increasing defense spending isn't just a Trump goal, it's been a HUGE Republican goal for, shit, ever. And ever since it was disclosed that Russia's nuclear stockpile is way bigger than ours, military people have been pissed off; we had an agreement to stop the nuclear arms race, but Russia has thrown that out the window.