U.S. President Donald Trump has wielded the powers of the presidency like a sledgehammer during his second term—especially in foreign policy—and frequently bypassed Congress. From launching the Iran war and ordering strikes on alleged drug trafficking boats near Latin America, to the operation that led to the capture of Venezuelan President Nicolás Maduro, Trump has repeatedly taken major military action without congressional approval.

With Republicans controlling Congress in Trump’s second term so far, Democrats have been extremely limited in their capacity to challenge the White House on this and many other fronts. But that’s about to change. Democrats won majorities in the House and Senate in Tuesday’s midterm elections, with stunning upsets in races nationwide. This opens the door for Democrats to steer the United States in new directions on a range of key foreign policy issues after the new Congress is sworn in early next year.

Democrats will have control over the appropriations committees in both chambers and oversee the drafting of annual military and foreign aid spending bills. This far from guarantees that Democrats will get their way, but the power of the purse will grant them considerable influence and negotiating power. Ahead of the midterms, top Democrats in Congress said that they would move to cut funding for the Iran war if they regained power. Now, a Democratic-controlled Congress will be able to leverage funding and make good on this pledge.

“Attaching a funding prohibition to a must-pass piece of funding legislation” would be the most effective “mechanism for forcing an end” to either the Iran war or boat strikes, Brian Finucane, a senior advisor at the International Crisis Group and a former attorney advisor at the State Department, told Foreign Policy.

As a potential model to follow, Finucane pointed to the example of Congress nearly forcing a government shutdown in 1973 to end then-President Richard Nixon’s bombing of Cambodia. If they’re willing to “play hardball” in this fashion and have the “political will,” then Democrats in the new Congress could probably “shut down” both the Iran war and the “lawless boat strikes,” he said. Experts have emphasized that the strikes on the alleged drug boats are illegal under both domestic and international law—an assessment that’s shared by leading congressional Democrats.

Democrats will also be taking control of Congress amid an evolving debate in Washington over what the next chapter of U.S. engagement in the Middle East should look like, fostered in part by the significant damage that U.S. bases in the Gulf have sustained amid the Iran war.

“Our bases there are going to need to be rebuilt or moved elsewhere. They’ve been heavily hit by Iran. That’s an appropriations issue 101,” Joshua Shifrinson, a professor at the University of Maryland’s School of Public Policy and an international security expert, said. Democrats will be able to “move the needle” on the issue of the U.S. presence in the Middle East by virtue of the fact that decisions will have to be made over whether to direct funding to rebuilding damaged installations or moving them elsewhere, Shifrinson added.

Similarly, the appropriations process will also make the needle movable when it comes to the future of the U.S. presence in Europe and its policy toward Ukraine, Shifrinson said. Democrats have fervently opposed Trump administration plans to reduce the U.S. military footprint in Europe, and have expressed outrage over the White House’s lack of support for Kyiv and recent efforts to reduce economic penalties for Moscow amid the Russia-Ukraine war. Much like Iran and the boat strikes, congressional Democrats are likely to use funding as a bargaining chip to challenge Trump on both issues. Democrats also signaled that regaining a majority would help speed up the passage of new aid packages for Ukraine, which have historically garnered bipartisan support.

The new Congress will still face significant constraints in its ability to counter Trump, and he’s vowed to charge ahead with his agenda regardless of the results. Trump is likely to continue leaning heavily on executive orders—which he’s done even as Republicans have controlled Congress—and has said he’ll veto Democratic legislation that he opposes. Given the immense political divide in the United States at present, Democrats will be unlikely to have the necessary support from Republicans to override Trump’s veto, which requires a two-thirds supermajority vote in both the House and Senate.

Despite such challenges, there are still other ways the incoming Democratic Congress can shape U.S. foreign policy beyond appropriations or legislation. Oversight is poised to play a particularly big role in how Democrats could shape U.S. foreign policy moving forward. Thanks to their big wins on Tuesday, Democrats will soon control powerful congressional committees with the ability to launch investigations, convene hearings, and issue subpoenas.

Democrats “can and should” use the “investigative powers of controlling committees to call hearings on any number of issues, ranging from Iran war oversight to foreign influence over U.S. policy, which would include corruption by the Trump family or potentially illicit foreign dealings,” Shifrinson said. “High-level investigations of all these facets of foreign policy … are very likely going forward.”

Trump has faced allegations from Democrats of using the power of his office to facilitate deals with foreign governments that are advantageous to his family and their business interests. This is likely to be a “substantial theme for oversight in the House and potentially in the Senate,” Finucane said. Democrats have already “not so subtly” indicated “that this is coming down the road” with letters to the administration. The administration’s “various dealings with Venezuela, including the oil sector,” are poised to be a topic of particularly aggressive oversight by congressional Democrats, he added.

Rep. Robert Garcia, who is now set to become chair of the House Oversight Committee, has pledged to investigate the Trump family for alleged crimes. On Tuesday night, he issued a blunt warning: “Lawyer up.”

Additionally, Senate Democrats could use their majority to block or delay national security nominees that they consider unfit for their prospective roles or as a means of bringing the Trump administration to the negotiation table on other issues.

There are also indications that Democrats will use their new oversight authorities to pursue impeachment proceedings against administration officials, with Defense Secretary Pete Hegseth at the top of the list of possible targets. Democrats have been adamant that they want more answers on the decisions and failures surrounding the Iran war. Holding hearings on the war will put an uncomfortable spotlight on the administration—and the Republican Party more generally—and could tee up Democrats to keep using Iran as a line of political attack in the leadup to the 2028 presidential election.

There’s also the possibility that Democrats will be able to bring at least some Republicans in Congress to their side on foreign policy issues like the Iran war, given its undeniable influence on the midterm results. Trump himself conceded that the Iran war was a “piece” of why the GOP lost. Meanwhile, Democrats could use their new authority in Congress to push for legislative reforms that would aim to prevent future presidents from taking foreign-policy actions similar to Trump’s. Such efforts would likely be vetoed, but they could help set the stage for important changes under later administrations.

“We’re really at a generational high point in terms of the political salience of these war powers issues, because Americans can feel the consequences of the president going to war lawlessly,” Finucane said. The 1973 War Powers Resolution “unfortunately failed to stop Trump from embarking upon this military misadventure” with Iran, he added, and Democrats “need to start laying the groundwork for structural reform to prevent further such a catastrophe.”