Donald Trump's return to the White House is set to reshape US foreign policy, promising potentially radical changes on multiple fronts as parts of the world are gripped by war and uncertainty, writes the BBC.
During the campaign, Trump made broad policy statements, often without concrete details, based on the principles of non-interventionism and trade protectionism - or, as he calls it - "America first".
Amid parallel crises, his victory foreshadows one of the most significant potential disruptions in Washington's approach to foreign affairs in recent years.
The BBC said they could provide some framework for his likely approach to different segments based on his comments during the campaign and his previous tenure from 2017 to 2021.
Russia, Ukraine and NATO
During the campaign, Trump repeatedly stated that he could end the war between Russia and Ukraine "in a day." When asked how, he suggested brokering an agreement, but declined to give details.
A research paper written in May by two of Trump's former national security chiefs suggests that the US continue supplying Ukraine with weapons, but make the support conditional, with a demand that Kiev begin peace talks with Russia.
In order to attract Russia, the West would promise to delay Ukraine's long-desired entry into NATO. The former advisers said Ukraine should not give up hope of recapturing all its territory from Russian occupation hands, but should negotiate on the basis of current front lines.
Trump's Democratic opponents, who accuse him of getting close to Russian President Vladimir Putin, believe that his approach would be an act of surrender to Ukraine and threaten all of Europe.
He has consistently emphasized that his priority is to end the war and stop the drain of American resources.
It's not clear how much the view expressed in the work of former advisers reflects Trump's own opinion, but it likely provides guidance on the type of advice he will receive.
His "America First" approach to ending the war also extends to the strategic question of the future of NATO, the transatlantic military alliance created after World War II, originally as a safeguard against the Soviet Union.
NATO today has 32 countries, and Trump has long been skeptical of the alliance, accusing Europe of relying on America's promise of protection for free.
Whether he would actually withdraw from NATO, which would represent the most significant change in the transatlantic defense relationship in a hundred years, remains a matter of debate.
Some of his allies suggest his tough stance is just a negotiating tactic to get alliance members to meet defense spending guidelines.
However, the reality is that NATO leaders will be seriously concerned about what his victory means for the future of the alliance and how its deterrent effect will be perceived by enemy leaders.
Near East
As with Ukraine, Trump promised to bring "peace" to the Middle East - meaning he would end the war between Israel and Hamas in Gaza and the war between Israel and Hezbollah in Lebanon - but did not say how.
He has repeatedly said that if he had been in power instead of Joseph Biden, Hamas would not have attacked Israel because of its policy of "maximum pressure" on Iran, which finances the group.
More broadly, Trump would probably try to return to that policy, which included the withdrawal of the US from the Iran nuclear deal, the imposition of stronger sanctions against Iran and the liquidation of General Qasem Soleimani - Iran's most powerful military commander.
In the White House, Trump has pursued strongly pro-Israel policies, naming Jerusalem the capital of Israel and moving the US embassy there from Tel Aviv — a move that delighted Trump's Christian evangelical base, a key group of Republican voters.
Israeli Prime Minister Benjamin Netanyahu called Trump "the best friend Israel has ever had in the White House."
But critics argue that his policies have had a destabilizing effect on the region.
The Palestinians boycotted the Trump administration, because Washington did not support their claims to Jerusalem - the city that forms the historical center of the national and religious life of the Palestinians.
They were further isolated when Trump brokered the so-called "Abraham Accords," which led to a historic deal to normalize diplomatic relations between Israel and several Arab and Muslim countries. They did this without requiring Israel to accept a future independent Palestinian state as a neighbor - the so-called two-state solution - which had previously been a condition of Arab countries for such a regional deal.
The countries involved in the agreement gained access to advanced American weapons in exchange for recognizing Israel.
The Palestinians have been left at one of the most isolated points in their history by the only power that can really apply pressure on both sides of the conflict - further weakening their ability, as they see it, to protect themselves on the ground.
During the campaign, Trump repeatedly stated that he wanted the war in Gaza to end.
He has a complex, sometimes dysfunctional relationship with Israeli Prime Minister Netanyahu, but he certainly has the ability to put pressure on him.
It also has a long history of strong relations with the leaders of key Arab countries that have contacts with Hamas.
It is not clear how he would balance the desire to strongly support the Israeli leadership while simultaneously trying to end the war.
Trump's allies have often portrayed his unpredictability as a diplomatic asset, but in the Middle East, at a time of major crisis of historic proportions, it is hard to predict how that might play out.
Trump will have to decide how — or whether — to continue the diplomatic process begun by the Biden administration to secure a ceasefire in Gaza in exchange for the release of hostages held by Hamas.
China and trade
America's approach to China is its most important strategic foreign policy issue—and the one with the greatest ramifications for global security and trade.
While in office, Trump labeled China a "strategic competitor" and imposed tariffs on certain Chinese imports into the US, prompting a response from Beijing with tariffs on US products.
Efforts to defuse the trade dispute were present, but the Covid pandemic destroyed this possibility, and relations worsened when the former president called Covid the "Chinese virus".
Although the Biden administration has claimed a more responsible approach to China, it has, in fact, retained many of Trump's import tariffs.
Trade policy has become closely tied to US domestic voter perceptions of protecting US manufacturing jobs – even though the long-term decline in jobs in traditional US industries like steel is due not only to global competition and the relocation of manufacturing, but also to automation and changes in manufacturing processes.
Trump praised Chinese President Xi Jinping as "brilliant" and "dangerous", and a highly effective leader who controls 1,4 billion people with an "iron fist" - which his opponents interpreted as Trump's admiration for "dictators".
The former president is likely to move away from Biden's approach of strengthening US security partnerships with other regional countries to rein in China.
The US has withheld military aid to self-ruled Taiwan, which China sees as a breakaway province that will one day come under Beijing's control.
Trump said in October that if he were back in the White House, he would not have to use military force to prevent China's blockade of Taiwan because President Xi would know he was "crazy," and would impose crippling tariffs on Chinese imports if that happened.
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