Republican leaders in the House of Representatives undercut a bipartisan effort to end U.S. involvement in Yemen by sneaking a measure that would kill an anti-war resolution into a vote about wolves.

On Tuesday night, the Republican-led House Rules Committee voted to advance the “Manage Our Wolves Act,” which will remove gray wolves from the endangered species list. The Rules Committee waived all points of order against the bill and voted to advance it to the floor.

The catch: Republicans inserted language that would block a floor vote on whether to direct President Donald Trump to end U.S. involvement in the Saudi- and UAE-led intervention in Yemen. The intervention has been highly destructive, flattening homes, roads, markets, hospitals, and schools, and leading to the world’s largest humanitarian crisis.

On Wednesday evening, the House approved the rule 201-187, largely on party lines, successfully blocking a vote on the Yemen resolution.

In September, Rep. Ro Khanna, D-Calif., introduced the Yemen resolution, which would have directed the Trump administration to remove U.S. forces from “hostilities” related to the Saudi-led intervention. Because it invoked the 1973 War Powers Act, Khanna’s resolution was “privileged” under House Rules, meaning it could bypass a committee vote and, barring any interference from the powerful Rules Committee, get a vote on the floor. The Republican gambit caused Khanna’s resolution to be stripped of its “privileged” status, meaning that it did not come up for a vote on its own.

If the Yemen measure had come up for a vote, it would have been the first time a chamber of Congress, which is notorious for avoiding votes on issues of war and peace, took an up-or-down vote that could end U.S. involvement in the conflict in Yemen.