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Saudi Arabia's crown prince, Mohammed bin Salman, called on President Trump on Tuesday afternoon — and it was all smiles in the Oval Office.

“The relationship was, to put it mildly, was very, very strained during the Obama administration, and the relationship now is probably as good as it’s really ever been,” Trump said. The president made his usual complaints about Iran while sitting alongside the crown prince, an inveterate Tehran foe, and he bluntly celebrated $12.5 billion in finalized arms sales to the Saudis. The pair grinned as they examined a poster outlining some of the American weaponry on Riyadh's shopping list.

But a storm was brewing on Capitol Hill. A bipartisan group of senators attempted to force a vote on a bill that would curb American support for the Saudi-led military intervention in Yemen, as well as asserting more broad congressional oversight of America's wars. Successive presidents have entered new conflicts without congressional approval, invoking the powers granted to them by lawmakers after the Sept. 11, 2001, terrorism attacks. Now, a decade and a half later, some of those lawmakers are citing the Saudi campaign against Yemen's Houthi rebels as a good place to start reining in the president's mandate.

After hours of debate, opponents of the legislation narrowly won a vote to table the resolution, effectively killing it for the time being. Still, it was a sign to the Saudis, who have placed all their eggs in the Trump administration's basket, that not all of Washington is on their side.

“The intended message is that Congress is taking its constitutional role much more seriously in matters of war,” a senior aide to Sen. Bernie Sanders (I-Vt.), one of the co-sponsors of the bill, said to Today's WorldView. “Allies should understand that U.S. support is not open-ended and that Congress will intervene when there is evidence of rights abuses and war crimes violations.”

Mohammad happens to be the main architect of Riyadh's war in Yemen, which it launched in 2015 alongside a coalition of regional allies. The suffering in the three years since has been hideous, and the toll is still difficult to measure.

Aid agencies estimate that at least 5,100 civilians have been killed, though the actual figure could be more than double that number. About 22 million Yemenis — more than two-thirds of the population — are in need of humanitarian aid; 8.4 million Yemenis, or about a third of the population, are believed to be on the brink of famine. The catastrophic conditions in Yemen spawned the worst cholera outbreak in modern history and an ongoing outbreak of diphtheria.

There is plenty of blame to go around. But the Saudis, as allies of the West and self-styled agents of regional stability, deserve to be singled out for particular criticism. The Saudi coalition has bombed Yemen more than 16,000 times over the past three years, with about one-third of the strikes hitting non-civilian targets. Rights groups and U.N. experts allege that the Saudi coalition could be guilty of war crimes. Meanwhile, Riyadh's blockade of Yemen's ports has in part provoked the staggering shortages of food, medicines and basic goods that have contributed to the collapse of Yemen's already enfeebled state infrastructure.

The Saudis argue that their campaign is required to check Iran, which backs the Houthis, and bring order to a strategically pivotal country on their southern flank. They also point to efforts they’ve made both to alleviate Yemeni suffering with humanitarian aid and better protect civilians.

As my colleagues reported, some Trump administration officials agree that the Saudis must push back against Iran. Other analysts in Washington argue that three years of bloodshed and chaos have only played further into Iran's hands.

In recent weeks, as resistance to the Saudi campaign has grown in Congress, the Trump administration launched a concerted offensive against the Yemen war-powers bill. “New restrictions on this limited U.S. military support could increase civilian casualties, jeopardize cooperation with our partners on counterterrorism and reduce our influence with the Saudis,”  Defense Secretary Jim Mattis wrote in a letter last week to Senate Majority Leader Mitch McConnell (R-Ky.), another opponent of the legislation.

Administration officials also attempted to suggest that U.S. support for the Saudi-led coalition — which includes intelligence-sharing, refueling support for coalition aircraft and the supplying of munitions found to have allegedly killed Yemeni civilians — does not constitute direct involvement in hostilities. That is a claim met with disbelief by critics.

“The U.S. government claims that it’s not engaged in hostilities unless U.S. troops are on the ground being shot at by the enemy,” said Sen. Mike Lee (R-Utah), another co-sponsor of the war-powers bill. “It stretches the imagination, and it stretches the English language beyond its breaking point, to suggest the U.S. military is not engaged in hostilities in Yemen.”

Even some opponents of the bill recognized that the status quo is untenable. “We talked about the importance of our relationship, no doubt,” Sen. Bob Corker (R-Tenn.), chairman of the Senate Foreign Relations Committee, said in a statement from the Senate floor after meeting with Mohammed on Tuesday. “But we strongly, strongly pushed back on what is happening right now in Yemen and asked them to take strong corrective actions.”

Meanwhile, Mohammed is being courted in Washington by U.S. arms companies hoping to sell tens of thousands of precision-guided weapons to both the Saudis and the Emiratis. Yet Trump said next to nothing about Yemen during the their meeting, let alone the prospect of bringing the war to an end. Most analysts suggest there’s no military solution to the conflict, which involves a thicket of factions with competing interests and tangled allegiances.

“The most the Saudis can hope for is prolonged guerrilla warfare in the inhospitable northern highlands,” wrote Robert Malley and April Longley Alley of the International Crisis Group, urging the Saudis to conclude their campaign. “This best-case military scenario would continue to bleed Saudi Arabia financially, erode its international standing and intensify hostility toward both the kingdom and its U.S. ally in these areas, all the while deepening Yemeni misery.”

“The conduct of hostilities on both sides has been abysmal and international humanitarian law has been constantly violated,” said Filippo Grandi, the U.N. high commissioner for Refugees, speaking to Today's WorldView on Tuesday about Yemen. “And, frankly, I'm not optimistic. I don't see any trend toward a political solution.”

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