Donald Trump's return to the White House will reshape American foreign policy, promising potentially radical changes on multiple fronts as parts of the world are gripped by war and uncertainty.

During the election campaign, Trump made general policy promises, often without specific details, based on the principles of non-interventionism and trade protectionism – or as he calls it, "America first".

His victory signals one of the most significant potential breaks in Washington's approach to foreign affairs amid parallel crises in recent years.

During the campaign, Trump repeatedly said that he could end the war between Russia and Ukraine "in a day."

Asked how, he suggested mediating the deal but declined to give specific details.

A research study written by two of Trump's former national security chiefs said in May that the United States should continue sending weapons to Ukraine but condition support on Kiev entering into peace talks with Russia.

To interest Russia, the West will promise to delay the much-desired entry of Ukraine into NATO.

Former advisers said Ukraine should not give up hope of returning all its territory under Russian occupation, but should negotiate based on the current front lines.

Trump's Democratic opponents, who accuse him of cozying up to Russian President Vladimir Putin, say his approach to Ukraine is tantamount to surrender and will endanger all of Europe.

He has repeatedly maintained that his priority is to end the war and stop the drain on American resources.

His "America First" approach to ending war also touches on the strategic question of the future of NATO, the all-for-one, one-for-all transatlantic military alliance originally established after World War II as a bulwark against The Soviet Union.

NATO now has more than 30 countries, and Trump has long been skeptical of the alliance, accusing Europe of "freewheeling" at the expense of American protection.

Whether he will eventually withdraw the US from NATO, which would represent the most significant shift in the transatlantic defense relationship in nearly a century, remains a matter of debate.

Some of his allies suggest his tough stance is just a negotiating tactic to force member states to meet the defense spending guidelines they have committed to.

But the reality is that NATO leaders will be seriously concerned about what his victory means for the future of the alliance and how its chilling effect is perceived by enemy leaders.

As in the case of Ukraine, Trump promised to bring "peace" to the Middle East – hinting at an end to the war between Israel and Hamas in Gaza and the war between Israel and Hezbollah in Lebanon, but did not say exactly how.

He has repeatedly said that if he had been in power and not Joseph Biden, Hamas would not have attacked Israel because of its policy of "maximum pressure" on Iran, which funds the group.

Overall, it is likely that Trump will try to return to that policy, which saw him pull the US out of the Iran nuclear deal, impose tougher sanctions on Iran and kill General Qassem Soleimani – Iran's most powerful military commander.

In the White House, Trump pursued a vigorous pro-Israel policy, declaring Jerusalem the capital and moving the US embassy there from Tel Aviv - a move that angered Trump's Christian evangelical base - a key Republican voting bloc.

Israeli Prime Minister Benjamin Netanyahu called Trump "the best friend Israel ever had in the White House."

But critics argue that his policies have had a destabilizing effect on the region.

Palestinians have boycotted the Trump administration over Washington's withdrawal from their claim to Jerusalem, a city that forms the historic center of national and religious life for Palestinians.

They were further isolated when Trump brokered the so-called "Abraham Accords," a landmark agreement to normalize diplomatic ties between Israel and several Arab and Muslim countries.

He did this without Israel having to accept a future Palestinian state alongside itself – the so-called two-state solution – which had previously been a condition of Arab countries for such a regional agreement.

Participating countries instead gained access to state-of-the-art US weapons in exchange for recognizing Israel.

The Palestinians were left at one of the most isolated points in their history from the only force that could really put pressure on either side of the conflict – further reducing their perceived ability to defend themselves on the ground.

Trump made several statements during the campaign saying he wanted the war in Gaza to end.

He has had a complex, sometimes dysfunctional relationship with Netanyahu, but he certainly has the ability to put pressure on him.

It also has a history of strong ties to leaders in key Arab countries with ties to Hamas.

It is unclear how he will manage to strike a balance between wanting to show strong support for Israel's leadership while simultaneously trying to bring the war to an end.

Trump's allies have often portrayed his unpredictability as a diplomatic asset, but in an extremely confrontational and volatile Middle East amid a crisis of historic proportions, it's not obvious how that would play out.

Trump will have to decide how — or whether — to resume the stalled diplomatic process launched by the Biden administration to obtain a cease-fire in Gaza in exchange for the release of hostages held by Hamas.

In these global topics, the question of his attitude towards China is also mentioned.

The US approach to China is its most important strategic area of ​​foreign policy – ​​and one of the most influential on global security and trade.

While in office, Trump declared China a "strategic competitor" and imposed tariffs on imports of some Chinese goods into the United States.

This prompted Beijing to retaliate by imposing import tariffs on some US goods.

There were efforts to de-escalate the trade dispute, but the covid pandemic made that impossible and relations soured when the former president called covid the "Chinese virus".

And while the Biden administration claimed to have taken a more responsible approach to China policy, it actually retained many of the Trump-era import tariffs.

Trade policy has become closely tied to the perception of US domestic voters about protecting US manufacturing jobs – although in fact most of the long-term declines in business in traditional US industries such as steel have more to do with factory automation and manufacturing changes than global competition and relocation.

Trump praised Chinese President Xi Jinping as a "brilliant" but "dangerous" and extremely effective leader who controls 1,4 billion people with a "firm hand" - part of what his opponents characterize as Trump's admiration for "dictators".

The former president is likely to move away from the Biden administration's approach of building stronger US security partnerships with other regional countries in order to rein in China.

The US has persistently provided military aid to independent Taiwan, which China views as a breakaway province that will eventually have to return to Beijing.

Trump said in October that if he returned to the White House, he would not have to use military force to stop China's blockade of Taiwan because President Xi knows full well that he would impose extremely damaging tariffs on Chinese imports if that happened.