The Real Culprit in Defense Spending: Strategic Hubris

Projection of power tends to create peace, that doesn't mean getting involved in every regional dispute. In order to be proficient at warfare, power must be exercised decisively when necessary.

"Walk softly and carry a big stick".

If you're living in a dangerous neighborhood it's better to be strong

Tough question. The down side is waiting until the situation escalates into a full blown war and then attempt to resolve it. Either way it costs a lot of money.