The aftermath of a bombing that destroyed three factories in Sana, Yemen, on Oct. 29, 2016. The Saudi-led coalition of Arab countries has bombed Yemen for more than two years in a war against Yemen’s Houthi rebels. Tyler Hicks/The New York Times

The battleground is Yemen, the poorest country in the Middle East. For nearly three years, Yemen has been under relentless attack from the region’s richest country, Saudi Arabia. Saudi bombing has created what the United Nations calls “the largest humanitarian crisis in the world.” More than half the population is hungry. Cholera is raging and may afflict 1 million people by the end of this year. A child dies from preventable causes every ten minutes. Saudi forces have blockaded Yemen’s main port, so almost no humanitarian aid can reach the victims.

This war could not proceed without American help. Missiles and bombs raining down on Yemen are made in the United States. American intelligence officers help Saudi pilots pick targets to attack. Most important, American tanker planes refuel Saudi fighter jets in flight, allowing them to carry out many more raids than they could if they had to return regularly to their bases. At the UN, American diplomats work to water down condemnations of Saudi Arabia, and to block investigation of possible war crimes.

Outrage at the American role in this war has led several members of Congress to propose a resolution that would pull the country out of “unauthorized hostilities” in Yemen. If they can force a vote, it may come in the first days of November. This will give Congress a chance to decide what role Washington should play in Yemen, in the multi-front Middle East War that we have been fighting since 1980, and in the world.

The resolution to pull US forces out of the Yemen war has bipartisan support, but so does the war itself. President Obama made the decision to plunge in, and President Trump has continued his policy. Both decided that the United States had to stand by its traditional ally, Saudi Arabia. Supporters of the war also make other arguments. They point out that forces we are helping to bomb in Yemen are supported by Iran, which we consider an enemy. Victory for those forces might be counted as a strategic loss for the United States. It could allow Yemen to become a base from which Saudi Arabia itself might be subverted. American involvement in this war is also a symbol that Washington stands by its allies and will use all means to crush terrorists in the Middle East.

The upcoming vote — if House leaders let it happen — will be about far more than Yemen. It is a test of whether Congress will continue allowing presidents to make decisions that push the United States into war, or whether it will awaken from its constitutional coma and assert its own right to do so. More than 200 years ago, when President Thomas Jefferson asked for authorization to send warships to fight pirates in North Africa, he said presidents are “unauthorized by the Constitution, without the sanction of Congress, to go beyond the line of defense.” Does that principle still apply, or does today’s rapidly changing “threat matrix” mean that Congress should stay out of the business of war? This question lies behind the upcoming congressional vote on Yemen.

So does an even larger one: What is the proper role for the United States in the post-Cold War world? Members of Congress instinctively shy away from contemplating such grand matters. The proposal they are now considering, which bears the unlovely name “House Concurrent Resolution 81,” forces them to do so. Some may hesitate to vote for it out of fear that they will be seen as weak in the face of terrorism, and that voters will punish them. Their fear is justified. America is a warlike state in which the military is revered and calling for peace is politically dangerous. As in any country, criticizing a war while it is underway strikes some as bordering on treason.

The argument on the other side is at least as potent. It is not simply that we are abetting the slaughter of Yemeni innocents, or that our Middle East wars are strategically unwise. Supporters of H.Con.Res. 81, as it is called in Washington, want to change the direction of not simply American foreign policy, but the United States itself. Propositions of that magnitude naturally frighten politicians.

War in Yemen has been bad for all parties, with the single exception of the American arms makers who supply the weaponry. Suddenly the proverbial silver lining is visible. This war gives members of Congress the chance to make a decisive choice. The vote on this resolution will be the political equivalent of the 2002 Senate vote authorizing war in Iraq. That vote reshaped history. Hillary Clinton’s support for the war resolution made her a pariah for one segment of the electorate, and contributed to her defeat in the 2008 election. The vote on H.Con.Res. 81 may have a similar effect. Any member of Congress who runs for president in 2020 will be judged in part by his or her choice in the coming days.