Cable news reporters have spent all weekend asking one US government official after another why we’re bombing Iraq and not Syria if we’re motivated by humanitarian concerns as Washington says.

I have yet to hear a straight answer, perhaps because the administration thinks a straight answer is undiplomatic. But I’m not a diplomat, and I can explain it point-blank.

So here it is. It’s real simple. The US is bombing Iraq right now because the psychopaths of the Islamic State (formerly ISIS) are attacking the Kurds.

Morally and philosophically, the death of every innocent person on earth—from New York City to Gaza—carries the same tragic weight. Lopping off the heads of Kurdish children in Iraq is not more reprehensible than cutting off the heads of children in Homs or Aleppo, but Syria is hostile and the Kurds are our friends, and that difference matters to government officials and foreign policy makers. If it didn’t, friendships and alliances would mean nothing.

The Kurds of Iraq are our best friends in the entire Muslim world. Not even an instinctive pacifist and non-interventionist like Barack Obama can stand aside and let them get slaughtered by lunatics so extreme than even Al Qaeda disowns them. There is no alternate universe where that’s going to happen.

Iraqi Kurdistan is a friendly, civilized, high-functioning place. It’s the one part of Iraq that actually works and has a bright future ahead of it. Refusing to defend it would be like refusing to defend Poland, Taiwan, or Japan. We have no such obligation toward Syria.

That’s it. That’s the entire answer. Washington is following the first and oldest rule of foreign policy—reward your friends and punish your enemies.