In the late 1990s, Joe Biden continued agitating for a wider U.S. war in the former Yugoslavia. In his eyes, the U.S., the United Nations, and Europe had all stood by and allowed a genocide to unfold in Bosnia. He was determined to convince the White House and NATO to act aggressively to confront what he charged was Slobodan Milošević’s next ethnic cleansing campaign. Throughout 1998-1999, Biden waged a tenacious campaign to sell the Clinton administration and his Senate colleagues on a preemptive bombing of Serbia, which he claimed was necessary to prevent killing and displacement operations against the ethnic Albanian population of Kosovo. Biden said “the objective will be to degrade [Milošević’s] military capability so significantly that he will not be able to impose his will upon Kosovo, as he is doing now.”

Belgrade’s position was that it was engaged in a fight against terrorist rebels, known as the Kosovo Liberation Army, or KLA, and that the allegations were propaganda and an attempt to undermine the country’s sovereignty. As Western governments began publicly accusing Milošević of ethnic cleansing, Belgrade found powerful allies in Russia and China to prevent a U.N.-sanctioned war. Kosovo, at the time, was a province of Serbia, and many nations considered the situation to be an internal issue and were reluctant to intervene militarily. U.N. Secretary-General Kofi Annan was disturbed by what he believed was a multiyear campaign of repression by Milošević’s government against Albanians in Kosovo but warned that unilateral action by the U.S. and NATO would constitute a violation of the U.N. charter. Biden routinely denounced the U.N. and scoffed at the notion that the U.S. needed its approval to take action.

By that time, there was a wide consensus within the NATO alliance that the U.N. had lethally failed in Bosnia and bore responsibility, particularly for the slaughter at Srebrenica. While Biden regularly denounced Milošević for preparing a genocidal war in Kosovo, he again made clear that it was not his sole motivation for demanding military action. “Let’s get something straight, it seems to me at the outset here. There’s been no talk about the U.S. interest here. We talk about humanitarian interests — it far exceeds the humanitarian interest,” Biden said in October 1998. “If I were president, I would just bomb him, and I mean that sincerely, and I would have the NATO allies come along.”

By March 1999, Biden’s campaign for war took on an air of imminence. “I think we will be bombing pretty soon,” he said on March 19. “We must move forward with a bombing campaign.” U.S. lawmakers were sharply divided on the war, with many Republicans and a handful of Democrats opposing it. Biden urged Clinton to sell the war to the public and to get congressional support. But Biden, who proudly boasted of his record on the War Powers Act, took a different position on a war he wanted: “Arguably, from the constitutional standpoint, [Clinton] doesn’t need it,” Biden said on the eve of airstrikes. “But I think it’s constitutionally wise, and I think it’s politically necessary.” He put the decision to go to war in grand terms. “At stake is our entire policy in Europe since the end of World War II to promote stability and democracy,” Biden said. “NATO’s credibility is on the line. We’ve warned Milošević many times to halt his fascist aggression.”

During the Senate debate on authorizing the war, Biden was asked why he opposed the 1991 Gulf War because it was done without proper congressional authorization but was minimizing such concerns regarding Clinton’s desire to go to war over Kosovo. “There is a big difference,” Biden replied. “The difference is, it is in the center of Europe, number one. Number two, if Europe in fact becomes destabilized, we are deeply involved in matters far beyond what is existing now.” He then said he was wrong not to support the 1991 Iraq War. “It turns out it made sense to move in the Gulf,” Biden said, “and I argue it makes sense for us to take this action now in the Balkans.”

In late March, Milošević’s government refused to accept an ultimatum that he allow 30,000 NATO forces to enter Serbia and effectively occupy Kosovo. The proposal also asserted that NATO forces had the right to move freely throughout the entire country, not just Kosovo, and that NATO personnel “shall be immune from all legal process, whether civil, administrative, or criminal.” The demands were even too much for former U.S. Secretary of State Henry Kissinger, one of the greatest warmongers in U.S. history. Kissinger criticized the ultimatum, calling it a “terrible diplomatic document” and “a provocation, an excuse to start bombing.” It seems that Kissinger’s analysis was correct, as a senior State Department official boasted at the time that the U.S. had “deliberately set the bar higher than the Serbs could accept.”

In the end, Biden’s camp won the day, achieving a non-binding 58-41 Senate vote to support the use of military force, despite the fact that the Clinton administration refused to comply with the requirements of the War Powers Act. In a rebuke of Biden and the White House, the House of Representatives voted against a war resolution by a razor slim majority of one vote.

On March 24, 1999, ignoring opposition from the U.N. and a sizable number of U.S. lawmakers, the U.S. began what would become a 78-day NATO bombing campaign against Serbia and Montenegro that saw civilian targets regularly struck, 16 media workers killed when a TV station was bombed, and internationally banned cluster bombs used, including on a crowded market, in attacks that killed between 90 and 150 civilians. The U.S. also bombed the Chinese Embassy in Belgrade, killing three journalists.

As the bombs began dropping, Biden said the war was important to make clear “our ability to secure our interest anywhere in the world.” At least 450 civilians were killed in the airstrikes, though Serbian estimates put the number much higher. For Biden, the bombing was not enough. “I’ve been saying, we should go into the — on the ground; we should announce there’s going to be American casualties. We should go to Belgrade, and we should have a Japanese-German-style occupation of that country,” Biden said on NBC during the bombing. “It’s the only thing that will ultimately work.”

A month into the air strikes, as many House lawmakers demanded that the War Powers Act be invoked and refused to pass a resolution supporting the war, Biden joined Republican Sen. John McCain in proposing a counterresolution that would authorize Clinton “to use all necessary force,” including ground troops in Kosovo, despite no official declaration of war. “We should never take anything off the table once we’re in a war,” Biden said. The measure was tabled in the Senate and, by a substantial majority, the House voted to block the use of any Defense Department funds for ground operations.

Weeks into the bombing, the American Civil Liberties Union declared that Clinton’s military action “violates the Constitution and the War Powers Resolution because it was not authorized by Congress.” In a statement reminiscent of Biden’s own past declarations on congressional war powers, the ACLU’s legislative counsel said, “Launching a sustained military action is a decision that no one person in our democracy — including the president — can authorize.” On April 28, a month into the bombing, the House of Representatives rejected a resolution supporting continued airstrikes. Nonetheless, Clinton, with Biden’s backing, continued the war.

While Biden and his allies claimed that the war was necessary to prevent ethnic cleansing and mass killing operations, the overwhelming majority of Kosovo Albanians killed by Serbian forces were killed after the NATO bombing began. Milošević responded to the airstrikes by unleashing his forces and deploying great numbers of both conventional and special units as well as vicious paramilitaries in a “systematic and deliberately organized” mass killing and forced displacement operation. During the bombing, an estimated 700,000 Kosovo Albanians were forcibly displaced. “The NATO air campaign did not provoke the attacks on the civilian Kosovar population but the bombing created an environment that made such an operation feasible,” a U.N. commission on the war concluded. Two months into the bombing, Milošević was indicted by the International Criminal Tribunal for the former Yugoslavia for war crimes committed in Kosovo. He was the first sitting head of state to be charged by the tribunal. Despite numerous instances of NATO killings of civilians during the bombing, including the direct strike on a TV station and its use of internationally banned munitions, no U.S. or NATO officials were charged with crimes.

As the bombing came to a close in June 1999, Republican Sen. Mitch McConnell was asked if the War Powers Act was dead. “Yes,” he replied. “I don’t think any president has ever felt that it was constitutional. I think it’s essentially not functional. Nobody pays any attention to it.” While McConnell and many Republicans opposed the law long before the Kosovo bombing, Biden had given their drive for unchecked executive power ammunition.

In June, Serbian forces withdrew from Kosovo as U.S. and NATO ground troops moved in. Over the next several years, tens of thousands of Serbs and other non-Albanians were forced from their homes or fled in fear for their lives. “The inability to stop a new wave of ethnic cleansing in Kosovo, in spite of the presence of 40,000 armed [NATO] soldiers, was a major failure for the international community,” concluded a subsequent U.N. report. Dozens of Serbian monasteries and churches were damaged or destroyed, and Kosovo’s new leaders, including top figures from the KLA, began agitating for independence. Biden was a major supporter of the KLA, praising one of its leaders, Hashim Thaçi, as “the George Washington of Kosovo.” Thaçi, who became Kosovo’s first prime minister after declaring independence from Serbia in 2008, was later indicted for war crimes and crimes against humanity for his role in the ethnic cleansing of Serbs and other ethnic minorities from Kosovo before, during, and after the U.S.-led NATO bombing campaign.

As for Milošević, a year after the NATO bombing ended, he faced a popular uprising following his rejection of the results of the first round of the country’s 2000 presidential election. Amid sustained protests supported in part by the U.S. and other Western governments, Milošević was forced to resign. He was later arrested in a raid on his villa by members of his former special forces and extradited to the Hague war crimes tribunal, where he died in prison four years into his trial.

In 2016, as vice president, Biden visited Belgrade in an effort to convince Serbia to recognize Kosovo’s independence. He faced street protests, primarily orchestrated by right-wing nationalist parties and figures, against his role in the bombings. A sizable number of the protesters also held signs or shouted slogans supporting Donald Trump in his presidential campaign against Hillary Clinton. After meeting with Serbian Prime Minister Aleksandar Vučić, a former top Milošević ally and information minister, Biden offered a rare acknowledgement of the Serbs killed in the bombing. Reading from a prepared statement, he said, “I’d like to add my condolences to the families of those whose lives were lost during the wars of the ’90s, including as a result of the NATO air campaign in terms of responsibility.”