DOIN' WHAT COMES NATURALLY:

Iran is already fighting ISIS on the ground. This summer, when it looked like ISIS was about to take Baghdad, Iran sent its best military commander, Qasem Soleimani, to bolster the Iraqi defenses. He apparently succeeded, because there has been little subsequent talk of ISIS taking Baghdad. It is also possible that recent Iraqi Army successes are due to the helping hand of Iranian troops and training. Iran is also, of course, helping Basher Assad to fight ISIS in Syria.

U.S. aerial firepower and Iranian troops could defeat ISIS, but more crucially, Iran is also in a position to stabilize the region. Assad is a monster, but if the U.S. and Iran were allied, he might be pressured into sharing power with the anti-ISIS rebels after ISIS goes down; as it is, our unrelenting commitment to get rid of Assad is assuring that Syria will remain in a state of anarchy, a vacuum that only an ISIS-type entity will ever fill. If anyone can pressure both Assad and the Iraqi Shiites into sharing power with local Sunnis, it's an American-Iranian duo.

But there is another big, important reason for us to join with Iran: oil. The Iranian oil industry is currently restricted by U.S.-led sanctions that deprive it of Western technology and investment. With those sanctions removed, Iranian oil would begin to flow; if Iran helps stabilize Iraq, the effect will be multiplied.

A flood of Iranian oil would give the U.S. the ability to level much heavier sanctions against Russia, and would ensure global oil supplies in the event that a broader conflict in Eastern Europe disrupts Russian oil supplies. In other words, becoming friendlier with Iran would strengthen our hand against the suddenly aggressive Russians.

Beyond the short-term threats of ISIS and Russia, Iran and the U.S. are, if not natural allies, then at least not natural enemies. Despite still being a theocracy at the top, Iran is more democratic and modernized than any country in the region except Israel. Iran's public is less anti-American than most of our Arab allies, and Iran sends many students to study at American universities.

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