Basically, war gives the government an excuse for raising wages which is what leads to economic growth, at least in terms of rising living standards. Of course, the elites have to feel threatened enough or at least bribed enough to play along, at least for the duration. To be effective, the war has to require a fair bit of industrial production and large enough armies and long enough duration to have an impact on the workforce, which is why our most recent small scale wars have had little or negative impact.
It doesn't give than excuse to raise wages, it just makes it so there's more jobs because you suddenly have to start producing everything that you can go blow up. As such, this may be less common due to the advent of automated construction of different things related to war.
It's the weapon producers who make the "money" from war, which pays those who own stocks in the company. Or you have to be employed under their name.
Some civilian jobs can make money from it too, however, as military surplus stores will get orders from or have the doomsday preppers come and buy up lots of their stuff.
Or you can go serve in the military
But war shouldn't be a necessity for economic growth. Start making more electronics or start popularising other things! That's how money is made in America...
