Moments before the United States Senate voted to end US support for the Saudi-led bombardment of Yemen on Thursday, Bernie Sanders stood on the floor of the Senate and announced, “We are actually at a historic moment here in the United States Senate.”

“Forty-five years ago, the War Powers Act was passed,” explained the independent senator from Vermont, in a brief reflection on the attempt by a Vietnam War–era Congress to rein in the imperial presidency. “Today, for the first time, we are going to go forward, utilizing that legislation, and tell the president of the United States and any president, Democrat or Republican, that the constitutional responsibility for making war rests with the United States Congress—not the White House. Let us pass this resolution.”

The Senate proceeded to do just that, voting 56-41 in favor of the resolution Sanders proposed in February. For months, the measure was dismissed as an untenable challenge not just to presidential overreach but also to the tendency of Congress to avoid the moral high ground in matters of war and peace.

On Thursday, however, seven Republicans joined 49 Democrats in support of the resolution, as Sanders noted that senators “in a very bipartisan way have come together to say that the United States will no longer participate in the Saudi-led intervention in Yemen, which has caused the worst humanitarian crisis on Earth—with 85,000 children already starving to death. Today, we tell the despotic regime in Saudi Arabia that we will not be part of their military adventurism.”

Sanders was right to recognize the profound nature of this vote for the legislative and executive branches of a federal government where, especially on military matters, the constitutionally outlined system of checks and balances has rarely functioned since Donald Trump took office. Last February, the senator from Vermont issued a call to conscience regarding the crisis in Yemen. He argued aggressively, on moral and constitutional grounds, that the US role in a war that has spawned a humanitarian crisis could not be ignored.

Those arguments gained traction as concerns about President Trump’s allegiance to Saudi Crown Prince Mohammed bin Salman mounted following the murder of Washington Post columnist Jamal Khashoggi in the Saudi consulate in Istanbul. And in the waning days of the 115th Congress, the Senate that has often treated Sanders as an outsider answered his call with a resounding “yes.”

At a time when House Speaker Paul Ryan is thwarting a Yemen vote in that chamber, the success of the effort by Sanders and his allies (especially Connecticut Democrat Chris Murphy and Utah Republican Mike Lee) to force a vote is striking. The fact that the vote ended in a rare rebuke by a Republican-led Senate to a Republican president is even more notable. But what is most remarkable is the assertion of congressional authority with regard to military interventions and engagements.

No one assumes that the balance between the separated powers of the presidency and the Congress has been fully restored. Ryan is still preventing a House vote that might embarrass the president. Trump vows to veto any legislation that threatens his ability to align the US with the Saudis. And this is just one piece of the very large puzzle of American military entanglements in the affairs of distant lands. For instance, Ryan and his allies have continued to block bipartisan calls for rescinding the 2001 Authorization for the Use of Military Force that Congresswoman Barbara Lee (D-CA) has long identified as an “overly broad blank check for war.”

But the Senate’s vote for the Sanders resolution bends the arc in the right direction. And it could bend even further next month, when Democrats take charge of the House. Congressman Ro Khanna, the California Democrat who has led the fight for action in that chamber, says he will reintroduce the Yemen resolution as a top priority for the 116th Congress. “The House must do our duty the first week in January when we are back,” says Khanna. “There will be no excuses with Speaker Ryan no longer in the way.”

For peace groups and humanitarian organizations, which have mounted a #YemenCantWait campaign on social media in recent weeks, the Senate vote was welcome news, as was the prospect of a House vote in January.

“US support for the war has given the Saudi-led coalition both the material support and the political cover it has needed to sustain its brutal campaign in Yemen,” explained Paul Kawika Martin, the senior director for policy and political affairs with Peace Action. “This vote immediately diminishes US political support for the war and puts more pressure on Saudi Arabia and the United Arab Emirates to end their brutal tactics and negotiate an end to the war.… Beyond its significance for the people of Yemen, by successfully invoking the War Powers Act, this vote also heralds the beginning of the end of Congress’ abdication of its war powers after nearly two decades of endless war with no meaningful oversight from Congress.”