The United States has been engaged in a war of choice against Iran for nearly two months. Negotiations to end the military conflict are underway but are yet to reach a conclusion.
Meanwhile, the Republican-controlled Congress has rallied behind President Donald Trump as he has waged a major bombing campaign that has destabilized the global economy, further fractured traditional alliances, and arguably strengthened the very regime it promised to weaken—one that now understands its capacity to roil world markets by closing the Strait of Hormuz. The nuclear material and expertise that the regime possessed remains in the country. Even during the cease-fire, Senate Republicans blocked a Democratic proposal to impose tighter constraints on the president’s war powers.
Although serious questions have been raised about the president’s mental stability, thanks to his social media posts threatening to erase an entire civilization and later attacking the pope, the Republican congressional majority has generally remained silent. Unless Congress changes hands in the midterms, there is little reason for Trump to fear any shift in that posture. The congressional wing of the GOP has made a calculated bet that despite growing rumblings among MAGA influencers and sliding approval numbers, protecting the president and backing the war remains in the party’s political interest. The partisan imperative guides everything.
Republican support for the president’s policy in Iran should not be mistaken as the consequence of a surrender of legislative power. Congress retains its constitutional authority, including control over military appropriations, and could quickly force Trump’s hand if Republicans leaders choose to act. Just as Iran is a war of choice, congressional complicity is a choice as well.
There is another path forward, however. In 1973, after years of devastating war in Vietnam waged under Presidents Lyndon Johnson and Richard Nixon (a Democrat and a Republican), Sens. Clifford Case of New Jersey, a liberal Republican, and Frank Church of Idaho, a Democrat, used the power of the purse to prevent any resumption of military operations in Southeast Asia following the singing of the Paris Peace Accords. Though their amendment passed very late in the war, after roughly 58,000 Americans had already died, it remains a concrete model of what Congress can do to constrain presidential war-making when there is a will to act.
The legislative struggle to stop the Vietnam War was slow to take shape. When Johnson asked Congress for a broad resolution authorizing military force in August 1964 (the Gulf of Tonkin Resolution) and again when he escalated bombing and ground troop deployments in the spring of 1965, most Democrats—who controlled both chambers—stood behind him. They wanted to protect his political standing as the administration pressed forward with an ambitious domestic agenda: the Great Society. Additionally, they had no desire to hand Republicans an opening to paint them as soft on defense, as the GOP had done after China fell to communism during Harry Truman’s presidency in 1949.
Most Democrats also subscribed to the domino theory: the belief that if Vietnam fell to communism, other surrounding countries would as well. Public opinion, moreover, still favored the military campaign. So even as senior Democrats like Georgia’s Richard Russell privately warned Johnson of the dangers of U.S. involvement, the Democratic Congress continued to appropriate everything he asked for, through the defense budget and supplemental requests, to bankroll the war.
Serious cracks in congressional support appeared in February 1966, when Sen. William Fulbright, who had pushed through the Gulf of Tonkin Resolution by rallying Democratic support in the middle of an election year, convened televised hearings in which he and the Foreign Relations Committee grilled administration officials about the rationale for the war. Still, the appropriations kept flowing. Johnson and Secretary of Defense Robert McNamara remained confident that when they returned to Capitol Hill for more funding, the answer would be yes. They were right.
The first major battle over war funding emanated not from the left but from the conservative coalition of southern Democrats and Republicans who controlled most of the major committees in the House and the Senate. Resurgent after the 1966 midterms, this bloc found its voice in House Ways and Means Committee Chairman Wilbur Mills in 1967 and 1968 when he pressured the administration to choose between guns or butter; Johnson, Mills insisted, could not have both. But the driving force behind this high-stakes confrontation was less a desire to cut off money for troops fighting in Vietnam than to force the president to scale back his domestic programs.
Political conditions shifted dramatically in 1968. The Tet Offensive early in the year had revealed that war’s end was nowhere in sight, shattering any remaining optimism or confidence in the credibility of the administration’s assurances. The costs, in U.S. lives and dollars, were becoming undeniable, while the anti-war movement grew in size and confidence. With a Republican in the White House after November, congressional Democrats also had far less reason to shield the executive branch from scrutiny. Public opinion had swung dramatically against the war since Fulbright held his hearings two years earlier. More congressional Democrats were willing to use the power of the purse to force Nixon’s hand.
The sense of crisis intensified in the spring of 1970, when Nixon announced to the nation in a televised address on April 30 that ground operations would take place in Cambodia, targeting forces allied with North Vietnam. For months, the news media had been reporting on a secret bombing campaign based on leaks. Public outrage was widespread. Protests at Kent State University in Ohio ended with members of the National Guard killing four students.
On Capitol Hill, Sens. Church and John Sherman Cooper (a Kentucky Republican who had broken with the war), responded by teaming up to push for an amendment that would cut off funds for ground and air operations in Cambodia.
The Nixon administration mounted a fierce campaign to kill the proposal and to accuse its supporters of being unpatriotic. In early May, Nixon told his advisors that they should push their congressional supporters to say that “not supporting the President is sticking a knife in the back of the U.S. troops, and attacking us on this is giving aid and comfort to the enemy—use that phrase, because that’s what it really is.”
Despite Nixon’s best efforts, the Senate passed the Cooper-Church Amendment with 58 votes on June 30, 1970, prohibiting the administration from spending money on soldiers, air strikes, or any other kind of combat assistance in Cambodia. The amendment was attached to a foreign military sales bill that passed by 75 votes. “By adopting this amendment restricting future United States operations in Cambodia,” noted the editors of The New York Times, “the Senate moved at last to reassert the constitutional role of Congress in committing American forces to overseas military action.”
In the end, senators were forced to compromise on the final language. The House blocked the amendment in conference committee. The revised language of the amendment was successfully added to a foreign aid authorization bill in December 1970, which went into effect one month later. The final version was narrower, limiting the prohibition to ground troops in Cambodia and Laos, permitting air strikes to continue.
Anti-war activists had backed a far bolder proposal from Sens. George McGovern and Mark Hatfield, which would have required the president to withdrawal all forces from Vietnam within a year. Even so, the amendment was seen as significant: It marked first time Congress had voted to withhold funding for any part of the war. “The Cooper-Church Amendment, and the sentiment it represented,” the State Department’s William Bundy wrote in his memoirs, “continued to hang over the White House.” Meanwhile, proposed amendments and roll-call votes to end the war continued to multiply.
In 1972, New Jersey Sen. Clifford Case joined Church in attaching an amendment to a foreign-aid bill that cut funding for military operations in Southeast Asia (including North and South Vietnam, Cambodia, and Laos) unless authorized by Congress. The Senate made history by passing it, the first time that the upper chamber had voted to cut off funds for the war. The legislation to which amendment was attached did not pass, but it served as further evidence that Congress was growing serious about ending the war. The drive to stop the war was no longer the exclusive cause of grass roots anti-war activists on college campuses. The administration and congressional leaders were feeling the pressure.
After Nixon signed off on the Paris Peace Accords in January 1973, Congress moved quickly to ensure he could not renege on the deal. In June 1973, lawmakers in both chambers passed the Case-Church Amendment, which stated: “None of the funds herein appropriated under this Act may be expended to support directly or indirectly combat activities in or over Cambodia, Laos, North Vietnam and South Vietnam … by United States forces, and after August 15, 1973, no other funds heretofore appropriated under any other act may be expended for such purpose.” The final legislation, which Nixon signed into law on July 1, passed the House 325 to 86 and the Senate 73 to 16. It was the same day that the draft officially ended, and the United States switched to an all-volunteer force, another major policy shift that resulted from the fallout over the war.
By the time that the amendment became law, numerous Republicans, who had doubts about the war and felt like they were under political fire for the Watergate scandal, were willing to break with the Nixon administration and join Democrats in the opposition. Even Senate Minority Leader Hugh Scott declared that he could “no longer support U.S. bombing of Cambodia, or in or over any of the nations of Indochina. … Try as I may, I cannot bring myself to agree that continued U.S. bombing will aid in bringing peace to this battle-scarred country.”
The amendment was far from perfect. It came very late in the conflict, carved out exceptions for economic aid and certain military equipment until April 2015, and gave Nixon time to exploit the delay in implementation as he unleashed a punishing bombing campaign until the August deadline.
Regardless of the shortcomings, the Case-Church Amendment marked a pivotal moment: Congress had used its constitutional authority over the purse to halt presidential war-making.
Congress faces the same choice it confronted in the early 1970s. Republicans in the majority can continue to give Trump a free hand with military initiatives, in Iran and elsewhere, or it can reject the administration’s expanding operations overseas. The decision is theirs. Every time Republicans decline to use the most powerful tool at their disposal, they are actively endorsing what the president is doing. Given that there are not U.S. ground troops in the theater of combat, the decision would be less complicated in 2026 than it was between 1970 and 1973. The GOP has not abrogated its power, as some commentators argue, but the party is using its power to support the militarism.
Legislative spending decisions speak far louder than public statements and social media posts. For all the talk of a party that puts “America first” and is determined to limit overseas investment at a time when many Americans are struggling to get by, the budgetary choices being made on Capitol Hill tell a different story: The GOP is perfectly comfortable with ever-expanding and costly military commitments abroad. A generation of Republicans that claimed to reject the legacy of George W. Bush and his war in Iraq appears to be doubling down on exactly that legacy. Voters should be clear about what they are voting for this November.
The history of the Case-Church Amendment is a reminder that Congress can make a different choice—but only if it wants to.
