President Donald Trump used his second-ever presidential veto on Tuesday to reject a bipartisan congressional resolution opposing U.S. support for Saudi Arabia’s war in Yemen against Iranian-backed Houthi rebels.

(The president’s first veto was of a congressional resolution last month disapproving of his national emergency declaration at the border. That veto was later sustained when the House failed to muster the two-thirds majority to override it.)

The president called the Yemen resolution “unnecessary,” because the U.S. is not officially engaged in “hostilities” in Yemen — a similar explanation to the one given by President Barack Obama regarding U.S. support for the Libya war. (though with more direct American involvement). He also said the resolution encroached on his constitutional powers — though, in truth, it is the executive branch that has been encroaching on Congress’s war-making authority for several decades.

But there is also an important strategic reason for the veto. Iran, not Saudi Arabia, is primarily responsible for the civil war in Yemen, arming the Houthis to wrest control of the country away from the Yemeni government. The new Houthi regime has attacked Saudi Arabia directly. Iran reportedly sees the conflict as a relatively inexpensive way to threaten its Saudi rivals and force the Saudis to spend billions of dollars on defense in a conflict that has dented the Saudis’ image.

Moreover, Yemen sits on the eastern side of the Bab el-Mandeb strait — a key shipping lane for traffic through the Suez Canal. The U.S. Navy has a major base across the strait, in Djibouti — as do many other countries, including China. Allowing an Iranian proxy to command the eastern side of the strait, across from a crucial U.S. Navy asset that helps control piracy and terror, and where China is challenging U.S. dominance, would be foolish to the point of lunacy.

Congress, which did almost nothing to defend its constitutional war-making authority when Obama was in office, has now decided to oppose Trump over Yemen. The gesture is made easier by the fact that America’s ally in Yemen, Saudi Arabia, is so widely disliked (unlike Britain and France, who led the Libya war). The brutal murder of Saudi writer and activist Jamal Khasgoggi last year only reinforced Saudi Arabia’s bad image and complicated Trump’s efforts to mend ties with the regime — the better to pursue the cause of Israeli-Palestinian peace and prevent a nuclear-armed Iran.

There is no doubt that Saudi Arabia is a bad actor. It pays little heed to human rights and international humanitarian law. It supported and disseminated radical Islamic ideology that helped inspire the terrorists who attacked the U.S. on Sep.11, 2001. But Iran is no better — and is worse, in that it openly aims to destroy the U.S. and America’s key regional ally, Israel. It is also pursuing a nuclear weapon and actively supporting terrorism in the Middle East and worldwide.

Some critics contend Trump is risking the support of an “anti-war coalition” in his base. But the anti-war movement is largely a left-wing phenomenon. Those elements of Trump’s base that approve his criticisms of previous wars, such as the Iraq war, are not opposed to war as such, but rather to war without victory, or end. Trump would create more, not fewer, political problems for himself by giving up Yemen to Iran — even as his sanctions have Iran on the ropes.

For some members of Congress, the Yemen resolution is a principled objected to foreign entanglements. For most, it is a cheap way to criticize Trump. Few have been asked to explain why they are supporting an effective surrender to Iran that would endanger American lives and interests. That question must be asked if Congress tries to mount an override.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.