Thursday, the Turks forced down a Syrian airliner flying from Moscow to Damascus and removed what the Turks described as military equipment. An angry Moscow has protested.

And Israel? While nothing would please Israelis more than a strategic defeat for Tehran, Assad and his father kept the peace on the Golan for 40 years. And as the Sinai is turning into a no man’s land with Hosni Mubarak gone and the Muslim Brotherhood in power, might not the same happen on the Golan when Assad falls?

And how have the Turks benefited from their involvement? By siding against Assad, they made a mortal enemy of a friend. Assad in retaliation loosened the reins on Syria’s Kurds, whose kinsmen are 20 percent of Turkey’s population. The Alawites in Turkey, ethnic Arabs, number another 15 million. The hard line taken by President Recep Tayyip Erdogan is becoming increasingly unpopular with his people.

How long would Americans support an administration that embroiled us in this maelstrom?

In the last week, shells from Syria have landed on Turkish soil. Is the Syrian army doing this deliberately? That makes no sense.

Are these mortar shells landing in Turkey a result of artillery duels between the Syrian army and rebels? Or are the rebels doing it deliberately to provoke Turkey into entering the war?

The Turkish line toward Syria is growing more belligerent. Are the Turks seeking a clash with the Syrian army so Ankara can invoke Article 5 of the NATO treaty and force the United States to join Turkey in ousting Assad, if not on a march to Damascus?

In an Arab world that does not fondly recall an Ottoman Empire whose heartland Turkey was, that would not sit well.

The Syrian civil war could end suddenly with the fall of Assad. But it could also widen with Turkey and Hezbollah becoming directly involved, and Russia, Iran and Iraq sending military aid to prop up their ally. The whole region could go up in flames.

Yet what vital American interest is there in who rules in Damascus to justify yet another U.S. war in the Middle East?

While the Assads are despotic, George H.W. Bush made the father an ally in Desert Storm and Ehud Barak offered to return to Hafez Assad the Golan Heights in exchange for a peace deal.

If America has a vital interest in this multisided war, that interest is served by staying out, as we have done for its duration.

And how exactly have we suffered by not plunging in?