Iran is holding firm against a months-long US air war, and it's bad news for Washington, which is running low on missiles and out of good options.

• The US has crushed Iran tactically — dominating its skies and killing thousands of its troops — but hasn't broken Iran's will to keep fighting.
• Iran's hardline leaders have a far higher tolerance for pain and are betting America will quit first.
• The US is burning through its weapons fast, using up most of its long-range missiles and much of its air defense stock, raising fears it couldn't handle Russia or China.
• Trump has threatened Iran with total destruction many times and backed down each time, so Iran no longer takes the threats seriously.
• Iran is squeezing oil shipping, targeting US troops, and pressuring US allies like Saudi Arabia and the UAE, who are now cutting quiet deals with Tehran.

Outlook: With US midterm elections 90 days out and Trump unwilling to risk a ground war, Iran expects to simply outlast Washington and win by default.