1. United States The United States spends a whopping $612.5 billion on the military, more than the other nine countries’ budgets combined. It maintains a remarkably large army composed of over 1.4 million soldiers, and a further 800,000 reservists. To complement the active ground force comprising well-trained men and women in uniforms, its biggest advantage is that it is the world leader in aircraft production, with a fleet of 19 aircraft carriers, while the carriers operated by the world together sum up to 12.