If you're going to use a historical example, try one that actually has some relevance. The Japanese had to export a huge amount of resources to support their industrialization anyway. That was one of the reasons for their invasion of a good part of Southeast Asia. The Iranians are trying to maintain their military, which includes aging systems sold under the Shah's regime, while getting around the sanctions. If it comes down to it, the Iranian Air Force won't last that long.

But logic has nothing to do with this. Your world requires some imaginary enemy to fear, the belief that the barbarians are at the gates. That the hordes don't exist is irrelevant to your fears.
Sometimes I feel like my shadow's casting me