President Trump distilled his foreign policy into the phrase "America First." In practice, the result has often been friction with allies, withdrawal from international agreements and the scaling back of the leading international role the U.S. has played for generations.
President-elect Joe Biden wants to restore a more traditional U.S. posture: warmer relations with longstanding partners, a recommitment to organizations such as NATO, and a U.S. that's once again front and center on the global stage.
"The world does not organize itself," Biden wrote in a lengthy article in Foreign Affairs in March. "For 70 years, the United States, under Democratic and Republican presidents, played a leading role in writing the rules, forging the agreements, and animating the institutions that guide relations among nations and advance collective security and prosperity — until Trump."
Trump has refused to accept the election results. But Biden's election victory has been well-received around the globe, from supportive tweets by many foreign leaders to street celebrations. Still, turning his worldview into reality faces a host of challenges.
Some U.S. partners no longer see Washington as dependable. China is challenging the U.S. leadership role in Asia. The U.S. military is still bogged down in Middle East conflicts that Biden supported as a senator when they began nearly two decades ago.
The president-elect has his critics. Robert Gates, who was defense secretary when Biden was vice president, wrote in his memoir that Biden is a "man of integrity." But he went on to say, "I think he's been wrong on nearly every major foreign policy and national security issue over the past four decades."
Here's a rundown of where Biden stands on major issues:
Reconnecting with allies
One of Biden's first foreign policy moves is likely to be a diplomatic offensive aimed at patching up relations with allies, particularly in Europe.
Trump demanded that NATO members pay more for the collective security arrangement — and many now are. But Trump also provoked ill will by frequently questioning the value of NATO as well as the cost. Some countries in Europe and elsewhere began to rethink their reliance on the U.S. and consider alternatives.
Still, Biden can expect a generally positive response. Biden has a wealth of foreign policy experience and works from a well-established, mainstream playbook that will be familiar and reassuring to many U.S. allies.
"As president, I will do more than just restore our historic partnerships; I will lead the effort to reimagine them for the world we face today," Biden wrote in Foreign Affairs.
Trump pulled the U.S. out of the Paris climate accord, saying it placed an undue burden on the U.S. economy. Biden says the U.S. will rejoin the agreement on Day 1 of his administration.
Biden also says the U.S. will return to the World Health Organization, which Trump walked away from after the coronavirus pandemic hit. The president said WHO was controlled by China.
Trump also unilaterally withdrew from the Iran nuclear deal, which was negotiated by the U.S. and other world powers and signed in 2015, when Biden was vice president. As the U.S. left the deal, Iran has gone beyond some of the limits imposed on its nuclear program.
Biden says Iran "must return to strict compliance with the deal. If it does so, I would rejoin the agreement and use our renewed commitment to diplomacy to work with our allies to strengthen and extend it."
Wars in Afghanistan and Iraq
As a senator, Biden supported the U.S. wars in Afghanistan and Iraq. The U.S. still has several thousand troops in both of those countries as well as a small contingent in Syria.
But now he says, "It's long past time to end the forever wars, which have cost the United States untold blood and treasure. As I have long argued, we should bring the vast majority of our troops home from the wars in Afghanistan and the Middle East and narrowly define our mission as defeating al-Qaida and the Islamic State."
For Biden, this means keeping a small number of U.S. forces in the region to focus on counterterrorism.
"There is a big difference between large-scale, open-ended deployments of tens of thousands of American combat troops, which must end, and using a few hundred Special Forces soldiers and intelligence assets to support local partners," Biden said. "Those smaller-scale missions are sustainable militarily, economically, and politically."
Biden could face tough decisions relatively soon. A preliminary deal with the Taliban calls for the U.S. to remove its roughly 4,500 troops from Afghanistan by May.
The U.S. and the Afghan government are trying to work out a permanent peace agreement with the Taliban, but the violence in the country has not stopped.
As a senator and vice president, Biden was long part of the bipartisan approach that encouraged U.S. engagement with China in the hopes that Beijing would mature into a responsible global actor.
The U.S. mood has changed dramatically in the past few years, with Republicans and Democrats calling for a much tougher approach. Trump launched a trade war by imposing tariffs on Chinese imports, and overall relations have grown increasingly tense.
Biden says he'll also confront Beijing, though he hasn't spelled out his plans.
"The United States does need to get tough with China. If China has its way, it will keep robbing the United States and American companies of their technology and intellectual property," Biden wrote in Foreign Affairs.
The U.S. military now views China as the biggest long-term threat, and Biden supports efforts to strengthen U.S. security arrangements with partners in the region.
The U.S. should be "reinvesting in our treaty alliances with Australia, Japan, and South Korea and deepening partnerships from India to Indonesia," Biden said.
Taking on Russia
Trump's strange relationship with Russia, and his refusal to criticize President Vladimir Putin, has been a defining feature of his foreign policy as well as his entire presidency.
Biden minces no words when talking about Russia.
"We must impose real costs on Russia for its violations of international norms and stand with Russian civil society, which has bravely stood up time and again against President Vladimir Putin's kleptocratic authoritarian system," Biden wrote.
Nonetheless, the U.S. and Russia will have to cooperate on some issues. Biden says he'll pursue an extension of the New START treaty, which regulates the nuclear arsenals of the two nations. He'll need to work fast — the agreement expires in February.
Greg Myre is an NPR national security correspondent. Follow him @gregmyre1.