American foreign policy for over half a century was defined by its bipartisan nature, symbolized in the old adage that politics stopped at the water's edge.
But in recent years, foreign policy has become as politically charged as virtually everything else in American life, and when voters mail in their ballots or go to the polls, they'll face a stark difference between the Republican and Democratic nominee and their views of the world and the United States' place in it.
Relations with China
The relationship between the U.S. and China will define the 21st century, and after cozying up to its increasingly autocratic leader Xi Jinping, Trump has in recent months taken steps to disentangle the world's two largest economies and punish Beijing for its assertive behavior. China has responded in kind, leading to sky-high tensions that a Biden presidency will likely be unable to undo.
While Trump pulled punches in search of a major trade deal during his term, the "phase 1" agreement reached in January has largely fallen apart, especially after the coronavirus pandemic. Former advisers like John Bolton have warned Trump will make concessions to win a new deal, but the president has promised to keep a tough stance.
That's been evident in some unprecedented moves in the last nine months that have fundamentally changed U.S.-Chinese relations. Trump has sanctioned the Chinese telecom giant Huawei and its officials and pushed other countries to ban it from their 5G networks, while moving to ban TikTok and WeChat, two highly popular Chinese apps, from the U.S. market.
He ended Hong Kong's special status under U.S. law after China's crackdown on democratic protests there and a new national security law that tightens its control. He declared American opposition to Chinese maritime claims in the South China Sea and unleashed sanctions over it, as well as on officials and firms supporting China's oppression of Uighurs and other Muslim ethnic minorities in Xinjiang province.
His latest moves have really rattled the Chinese -- demonstrating strong support for Taiwan. The administration announced Wednesday another $1.8 billion in arms sales to Taiwan, which China considers a breakaway province, with more arms sales and possibly trade talks in the pipeline.
Biden's advisers have actually said there are some measures they support in Trump's China policy, but fault his erratic statements and singular pursuit of a trade deal. They vow to keep up the economic and diplomatic pressure on Beijing over its trade practices, technology theft and human rights abuses -- and have even refused to say whether they'd repeal the tariffs Trump has placed on about two-thirds of Chinese imports to the U.S.
But Biden has also emphasized working with China on issues of international concern, like climate change and North Korea's nuclear arsenal, and called for using less bellicose rhetoric. Instead, he's backed ending tariffs on U.S. allies Japan, South Korea and the European Union, seeking to bring them together in a trade coalition against Beijing.
Iran nuclear deal
The Iran nuclear deal has become one of the most divisive issues in U.S. foreign policy, with Obama administration officials defending it as critical to stopping Iran from developing a nuclear bomb and Trump administration officials blaming it for Iran's aggression in the region.
After nearly four years in office, Trump has not been able to fully kill the deal, with continued international inspections of Iran's nuclear sites and meetings of the deal's remaining signatories. Instead, the U.S. is isolated at the United Nations in trying to return sanctions, even as Iran has violated nearly all the limits on its nuclear program, stockpiling more uranium enriched at higher levels using more centrifuges.
If Trump is reelected, top advisers like national security adviser Robert O'Brien say they believe Tehran will be unable to endure four more years of his "maximum pressure" campaign of stringent sanctions and will negotiate for a "better" deal that includes Iran's ballistic missile program and regional behavior.
But Iranian leaders have said they will not negotiate with Trump, instead raising pressure on the U.S. with attacks through proxies in the region and on the EU through nuclear brinkmanship. Trump has responded with military force, including the strike that killed Iran's top general, Qassem Soleimani, just days into 2020. That aggressive response is likely to continue, with Trump warning Iran will never obtain a nuclear bomb on his watch and leaving military use on the table as a means to do so.
In contrast, Biden has vocally defended the deal his and Obama's administration negotiated. If Iran returns to "strict compliance" with the limits it's broken, he will rejoin the deal, he's said, and negotiate to strengthen and extend those limits.
But that would also be an uphill battle. Iranian officials have already demanded compensation for the sanctions that Trump has placed on Iran's economy and that have blocked the business that Tehran was supposed to secure under the nuclear deal. Getting Iran to return to compliance without that will require hard negotiations, and pushing them to accept new limitations will be even harder given how easily Trump tore up the old deal.
Beyond the nuclear deal, Biden has vowed to continue "targeted" sanctions for Iran's human rights abuses, terrorism throughout the region and ballistic missile program.
US in the Middle East
Trump campaigned on ending America's "endless wars" in Iraq and Afghanistan, and in the final weeks of the 2020 race, he's moved to draw down troops in both countries, even as they sink further into violence and political chaos. Biden has tempered that push, saying it's time to bring U.S. service members home, but arguing total withdrawal should wait until the conditions are right -- without specifying what those conditions are.
Elsewhere in the Middle East, Trump has brandished new agreements between Israel and two of its Arab neighbors as evidence of his role as a peacemaker. His top aides have promised other countries will soon follow, redefining relations in the Middle East -- a move that Biden has praised and tried to take credit for. But Biden's Israel policy, while offering continued strong military support, will likely moderate Trump's relentless boost of Prime Minister Benjamin Netanyahu and his continued annexation of Palestinian territory.
Instead, Biden may try to return the U.S. to its previous position as a more neutral arbiter between the Israelis and Palestinians, with strong pressure in the Democratic Party's left flank to support the Palestinians. He has also signaled a harder line on autocrats in the region, like Crown Prince Mohammed bin Salman of Saudi Arabia and President Recep Tayyip Erdogan of Turkey, for their human rights abuses and regional adventurism, in contrast to Trump's embrace of both men.
NATO and Western allies
Trump has spent four years browbeating NATO members to boost their defense spending, and while his comments have repeatedly undermined the alliance, aides like Secretary of State Mike Pompeo argue it has strengthened the western alliance by increasing states' defense capabilities. As Trump strikes an increasingly hostile tone on China, his administration would push NATO to challenge Beijing, along with other partners like Japan, Australia and India.
But there's strong concern that Trump would also fully sour on the alliance, which he famously called "obsolete" during the 2016 campaign, and withdraw during a second term. Bolton, his longest serving national security adviser, has warned it could happen, although Pompeo, who said recently he would stay during a second Trump term, has signaled it won't.
Biden, on the other hand, has made boosting NATO a centerpiece of his foreign policy platform, arguing Trump's bullying has damaged U.S. leadership. Beyond "restor[ing] our historic partnerships," Biden's campaign site says he will push NATO to take on new threats while deepening America's alliances elsewhere.
That plan also includes increasing investment in the U.S. diplomatic corps after Trump's years of proposed cuts, restarting U.S. leadership on climate change, ending Trump's strong-arming of allies like South Korea and Japan to pay more for hosting U.S. troops, and taking "steps to reinforce the democratic foundation of our country and inspire action in others."
North Korea's nuclear program
Trump's personal diplomacy with North Korea's Kim Jong Un was once his signature foreign policy move, but it's now all but fallen from headlines -- even while the threat from Pyongyang's nuclear arsenal continues to expand. Instead of laying out next steps, Trump has continued to tout North Korea's halt of nuclear and long-range missile tests as a security win.
His top aides have at times acknowledged that the dangerous threat remains, especially to U.S. troops and allied countries in the region. But they continue to express hope that North Korea will return to the negotiating table to dismantle its nuclear weapons program in exchange for sanctions relief and a "brighter future."
That flies in the face of Kim's statements for 10 months now about moving away from talks with Trump and maintaining his nuclear arsenal as a security deterrent.
In the face of that intractable problem, Biden has said he will keep U.S. and U.N. sanctions in place, push China and Russia to tighten their enforcement and also try to drive Kim's regime back to the table. Notably, he hasn't sworn off following Trump's footsteps into a meeting with Kim, but said he wouldn't do so until U.S. negotiators laid the critical groundwork for a meaningful agreement.