Many Americans find it hard to understand why the United States is involved in a war in Yemen, the poorest country in the Middle East.

In the face of criticism even from Democratic lawmakers, the best explanation from the Obama administration is that Saudi Arabia, a key U.S. ally, is threatened by the takeover in neighboring Yemen of Shiite rebels backed by Iran. At the other end of the conflict is an unelected Sunni government supported on the battlefield by Saudi Arabia, the United Arab Emirates and Bahrain, which have been U.S. arms customers. The U.A.E. lost a fighter-bomber over Yemen on Sunday; Bahrain lost a U.S. F-16 in December.

There is no reason for the United States to have taken sides in this intra-Islamic war. Yemen’s former authoritarian president, Ali Abdullah Saleh, was pushed out in 2012 after decades in office by a combination of Saudi Arabia, Yemeni elements and the United States. He is now backed by a well-armed militia and is fighting alongside the Shiite Houthis.

Al-Qaida and the Islamic State group are taking advantage of the chaos in the country to seize more territory.

The Saudis themselves acknowledge that they have no endgame for the Yemen war.  So far some 6,000 Yemenis are estimated to have been killed, including 3,000 civilians. Yemen never had much of an economy, and what little there was has been destroyed. An estimated 56 percent of its people are considered to be hungry.

If Mr. Obama would like to end involvement in one of America’s Middle East wars before he leaves office next January, Yemen should be high on the list. It is a pathetically poor country, and the United States has no reason to add to its misery by selling bombs, drones and aircraft to Saudi Arabia to hurt the Yemenis.