Trump closes 2019 with a stain as the third president in US history to be impeached yet also with perhaps his two biggest achievements on the international stage -- the US commando raid that killed the leader of the militant Islamic State group, Abu Bakr al-Baghdadi, and a new trade pact with Canada and Mexico.
But the year was also full of tosses and turns for the tycoon turned president.
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On his ambition to end the war in Afghanistan, he startled Washington by inviting the Taliban to talks, then declaring the talks dead, and finally resuming them.
On North Korea, where Trump has hoped to broker a landmark accord, a highly anticipated summit with leader Kim Jong Un ended in stalemate.
Trump later jump-started talks with a hastily arranged new meeting, but he ends the year with North Korea firing rockets and threatening a "Christmas gift" unless the United States offers concessions.
His efforts on Venezuela have had less whiplash but also little to show, with the United States leading Western and Latin American powers in January in declaring the illegitimacy of leftist leader Nicolas Maduro -- who remains in power despite concerted US support for the opposition and sanctions.
On one especially tumultuous issue, the trade war with China, tensions eased at year's end with a "phase one" mini-deal in which Trump backed off on some tariffs and Beijing pledged to buy more US goods.
But the underlying feud remains unsolved between the world's two largest economies, with the United States expected to press hard in 2020 on key concerns such as China's state subsidies.
In a rare issue that has drawn criticism from his Republican allies, Trump also sent mixed messages on Turkey, ordering a US troop withdrawal from Syria that paved the way for Ankara to attack US-allied Kurdish fighters before Trump pressured the NATO ally with sanctions.
Beyond the hotspots, Trump may have broken the most ground with his style, hobnobbing with some of the world's most autocratic leaders even as he clashes with many close allies, as seen in his testy exchanges at the December NATO summit.
He has torn through the international consensus by withdrawing from the Paris climate accord and a European-backed denuclearisation pact with Iran, and by unabashedly seeking to boost Israel's right-wing leader, Benjamin Netanyahu.
In a mirror of his domestic agenda in which slashing immigration is a top priority, Trump has cast himself as the unique leader who stands up to the long-accepted status quo.
Heading on his NATO trip, Trump's first words were not on the security challenges of Russia, Syria or Afghanistan but of allies he says contribute less than their fair share.
The 2020 White House campaign opens under the shadow of Trump's impeachment on December 18, when House Democrats voted overwhelmingly that Trump abused his power by pressuring Ukraine to dig up dirt on domestic rival Joe Biden.
Democratic presidential candidates have meanwhile focused on health care and other domestic issues.
But Brian Katulis, a senior fellow at the left-leaning Center for American Progress, called foreign policy the "sleeper issue" of the election with the theatrical Trump likely to find a way to put it at the forefront.
"This is a reality TV presidency. Even if he doesn't achieve major successes, he will claim that he has," he said.
"He will use other countries and their leaders as props in his re-election campaign."
Nile Gardiner, a former aide to British prime minister Margaret Thatcher who is now at Heritage Foundation, a conservative Washington think-tank, argued that Trump had achieved "significant successes."
"We have seen 99 per cent of ISIS territory taken away in Iraq and Syria. There's still a job to be done but this is a very, very big-scale achievement," he said.
"Trump's foreign policy is forward-looking and not isolationist," Gardiner said, adding that European leaders "are preparing for the very strong possibility of Trump's re-election."
Gardiner argued that Trump had also "significantly weakened" Iran, where anti-government protests erupted in November in the wake of sweeping US sanctions.
Critics say the hard line has been counterproductive by reducing Iran's compliance with the 2015 nuclear accord and encouraging the clerical regime to hit back in the region.
Just as he was being impeached, Trump achieved a major legislative victory when the Democratic-led House overwhelmingly backed his successor to the North American Free Trade Agreement.
The new United States-Mexico-Canada Agreement found rare common points between Trump and liberal Democrats generally opposed to free trade deals through measures such as strengthening labour standards in Mexico.
In hotspots such as Iran and North Korea, Trump will at least make the case that he has taken a different approach than his predecessors, Katulis said.
"It's hard to point to the actual successes of Trump foreign policy. It is really a world in disarray," Katulis said.
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"But facts be damned -- he will make a case that America's burden is less in the world, others have been doing more."
Trump's core narrative is that "foreigners have been taking advantage of America" -- and he will be eager to make national security a wedge issue in domestic politics, Katulis said.
"With Trump, you can expect the unexpected."
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