There are growing bipartisan concerns and warnings about the unrestrained power of presidents to take the republic into war. That worry has surfaced most recently with respect to U.S. military involvement in Syria and the looming danger of war with Iran. Both Barack Obama and Donald Trump committed U.S. military personnel to Syria, ostensibly to repel the terrorist threat that ISIS posed, but also to assist other insurgent forces attempting to overthrow Syrian dictator Bashar al-Assad. Obama and Trump did so without seeking (much less obtaining) a declaration of war—or even a more limited congressional authorization.

Those episodes are just the latest manifestations of what historian Arthur Schlesinger, Jr. labeled the imperial presidency more than four decades ago. Schlesinger worried that the ability of presidents to launch major military ventures on their own had grown steadily during the Cold War and had reached the point that it undermined the constitutional system of checks and balances. Matters have grown considerably worse since he expressed such concerns. Indeed, the reality of an out-of-control presidency regarding decisions of war and peace may well have reached the point where it cannot be reversed.

The emergence of an imperial presidency reflects both executive usurpation of the constitutional war power and congressional abdication of that power. The most crucial episode was Harry Truman’s commitment of U.S. troops to the Korean War in the summer of 1950. True, there had been earlier episodes of executive military missions with little or no congressional approval, especially interventions in Latin America during the first decades of the twentieth century. But there had never been anything close to the scale of the Korean War. Not only the two world wars, but smaller conflicts such as the Spanish-American War and the War of 1812, were authorized as the Constitution required: with a formal declaration of war. Yet Truman sent more than three hundred thousand U.S. military personnel to the Korean battlefield to wage a full-scale war that ultimately lasted more than three years and resulted in some thirty-six thousand American fatalities without even asking for such a declaration.

The flaccid congressional response to Truman’s violation of the Constitution was an omen of how subsequent Congresses would fail to defend the war power that the founders explicitly entrusted to the legislative branch. Members of the eighty-first Congress had an opportunity to strangle the imperial presidency in its cradle by impeaching the president if he persisted. But at this crucial moment, they flinched from confrontation. A repetition of the twin processes of usurpation and abdication became increasingly routine in future episodes.

It is doubtful that legislators failed to defend the prerogative of their branch because they believed Truman’s rationale for authorizing a massive military venture on his own. The president asserted that he did not need a declaration from Congress because the United Nations Security Council had approved the operation, and the Senate’s ratification of the UN Charter made the exercise of such authority legal. Indeed, Truman administration officials refused to call the Korean conflict a “war,” insisting instead that it was a UN “police action.”

The use of Orwellian euphemisms would become a staple of the imperial presidency. When Obama launched an air-and-missile barrage against the Libyan regime of Muammar el-Qaddafi in 2011, he and his advisers insisted that it was not a war, but a “ kinetic military action .” Naturally, Obama concluded that he did not need congressional approval for such an operation.

When the founders established the system of checks and balances in the Constitution, they assumed that each branch would jealously guard its powers. Why, then, did Congress fail to challenge Truman’s usurpation of the war power? One reason was sheer partisanship. The vast majority of Democrats in both chambers loyally lined up in support of their party’s leader. Most of the opposition to the Korean intervention came from conservative Republicans.

But GOP critics tended to be conflicted. Since the enemy in Korea was a Godless communist regime, and an ally of the Soviet Union and a newly communist China, right-wing legislators found it difficult to oppose an initiative to prevent the further spread of that odious doctrine. Prominent conservative Republicans such as Senators Robert Taft of Ohio, William Jenner (Indiana) and Kenneth Wherry (Nebraska) found themselves criticizing Truman’s unilateral exercise of presidential power, but endorsing the underlying mission. That was an extremely awkward position to sustain.

Finally, as with many later presidential wars, avoiding responsibility for the decision to go to war in Korea reduced the political risk to members of Congress. If the intervention turned out well, they could maintain that they supported the policy all along. If it turned out badly, then they could (as they ultimately did) brand it as “Truman’s war.” That cynical, opportunistic sequence would surface again when the Vietnam and Iraq wars began to turn sour.

But the rule of law and the health of the republic suffered a severe blow when the eighty-first Congress failed to fulfill its constitutional duty. There have been more than a dozen presidential wars since Truman set the precedent in Korea. In some cases, there has been nominal congressional input amounting to little more than Congress giving the president blank-check authority. The infamous 1964 Gulf of Tonkin Resolution for the Vietnam War and the Authorization for the Use of Military Force following the 9/11 attacks fall into that category. But presidents frequently dispense even with such façades. Reagan’s intervention in Lebanon, Clinton’s in Bosnia, and Obama’s in Libya and Syria were graphic examples. Indeed, Clinton surpassed even the executive branch’s usual contempt for Congress. He waged his military intervention in Kosovo despite a House vote declining to endorse that campaign.

Not only has congressional abdication of the war power led to a marked increase in the number of dubious wars America has waged, it has produced a dangerous overall expansion in presidential power. Truman again demonstrated the potential menace when, in the name of national security because of the ongoing Korean conflict, he seizedthe nation’s steel mills in April 1952 to thwart a strike that was disrupting production. Fortunately, the U.S. Supreme Court demonstrated on that issue the courage that Congress lacked regarding the war power. It struck down Truman’s latest power grab. Nevertheless, it was ominous that three justices were willing to ratify the president’s outrageous action. The incident itself confirmed that potential abuses of power by an imperial presidency would not be confined to foreign affairs.

The founders intended that no single person should have the authority to take the nation into the horrors of war. At the Constitutional Convention Elbridge Gerry of Massachusetts epitomize the majority view when he stated that he “never expected to hear in a republic a motion to empower the Executive alone to declare war.” And the delegates clearly believed that “declare” meant “authorize.”

We have paid, and will continue to pay, an awful price for the cowardly failure of the eighty-first Congress to defend the prerogatives of the legislative branch and stop the president’s usurpation of the war power. If a bipartisan majority had impeached Truman for his unconstitutional action in initiating a presidential war, his successors likely would have been wary of venturing down the path of an imperial presidency. One can only hope that the lost opportunity was not irreplaceable and that a future Congress will finally muster the courage and integrity that the eighty-first Congress so clearly lacked.