President Donald Trump's decision to withdraw US troops from northeast Syria has proven disastrous for the US's Kurdish allies and shaken global faith in the US's credibility.

It's opened the door to the resurgence of ISIS, handed Russia a major geopolitical victory, and catalyzed a humanitarian crisis in Syria.

The decision has virtually no political or strategic benefits, which begs the question: was the president motivated by something other than the US's national interests when he retreated from Syria?

Scroll down to read about Trump's myriad business and financial ties to Turkey.

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President Donald Trump's retreat from northeastern Syria has proven disastrous for the US's Kurdish allies in the region and shaken global faith in the US's credibility. The decision has opened the door to the resurgence of ISIS, it handed Russia a major geopolitical victory, and it's catalyzed a humanitarian crisis in Syria.

On the domestic front, Trump's decision prompted a swift, bipartisan rebuke in both chambers of Congress, including from top Republicans.

Trump's move has had virtually no political or strategic benefits, which begs the question: was the president motivated by something other than the US's national interests when he pulled troops from northeastern Syria and effectively handed Turkey a win on a silver platter?

"It's hard to explain Trump's actions in Syria through the prism of what's best for American national security," Sen. Chris Murphy of Connecticut told Insider on Tuesday. "So, we're searching for other explanations. What we know is that the president has business interests in Turkey."

Read more: These are the key players you need to know to make sense of the Trump impeachment inquiry

The Democratic senator, who sits on the Senate Foreign Relations Committee, said the situation underscores the need for Trump to release his tax returns: "The American people deserve to know the extent of the president's business interests overseas so that we know whether he's making foreign policy decisions in the best interests of the country or in the best interests of his family, bottom line."

Multiple other Democratic lawmakers, including Sen. Richard Blumenthal of Connecticut and Rep. Ted Lieu of California, have raised Trump's business links in Turkey to his Syria retreat.

Citizens for Responsibility and Ethics in Washington (CREW) has also voiced concerns. "We can't ignore that the president's decision to abandon the Kurds, despite widespread backlash, could have had something to do with the property he owns and profits from in Istanbul," the ethics group said in a recent tweet.

Trump has broken from other presidents in retaining ownership of his business empire and not placing his assets in a blind trust while in office.

Read more: 8 Trump officials made stunning revelations about how the president and Giuliani weaponized the State Department

Here's what we know about Trump's business ties in Turkey:

The Trump family has extensive business ties in Turkey, and Trump in a 2015 interview with Breitbart suggested there could be a conflict of interest.

"I have a little conflict of interest because I have a major, major building in Istanbul," Trump said at the time. "It's a tremendously successful job. It's called Trump Towers — two towers, instead of one, not the usual one, it's two."

Trump Towers Istanbul continues to generate revenue for Trump as part of the Trump Organization.

Ivanka Trump, the president's daughter and a White House adviser, traveled with her father to Turkey for the launch of Trump Towers Istanbul in 2012.

Ivanka directly thanked Erdogan in a tweet. Trump also tweeted about it a few times.

Erdogan called for having Trump's name removed from Trump Towers Istanbul in 2016, accusing then-presidential candidate Trump of Islamophobia. Trump had called for banning all Muslims from entering the US during his 2016 campaign.

Trump licenses his name to the owner of the building and made $1 million to $5 million in royalties in 2015 and 2016. And he made $100,001 to $1 million for 2017 and 2018, according to his financial disclosures.

Turkish business magnate Aydin Dogan owns the building. The Dogans invested $400 million in Trump Towers and Trump has boasted about their "great friendship."

The Trumps also have a close relationship with Mehmet Ali Yalcindag, Dogan's son-in-law, who's the president of the Turkish-American Business Council (TAIK).

In 2017, TAIK held a conference the Trump International Hotel in Washington, DC, which was attended by Commerce Secretary Wilbur Ross, according to NBC News.

Yalcindag in an interview last year expressed hope that Trump would make foreign policy decisions that give Turkey more power to address regional issues and problems near its borders (Syria borders Turkey). He signaled that businesspeople were ready to act to help alleviate tensions between Ankara and Washington.

Turkish officials have visited Trump properties 14 times, more than officials from any other country, according to a CREW analysis performed for NBC News.

There have also been four Turkish-government related events at Trump's hotel in Washington, according to CREW.

Trump has also been scrutinized for his financial interests in other countries, including Russia and Saudi Arabia. His frequent and repeated capitulation to the leaders of both countries has raised questions about whether the president was motivated by personal interests when dealing with them in an official capacity.

Trump's financial ties to Russia, in particular, were central to the former special counsel Robert Mueller's investigation into Russian interference in the 2016 election. They're also a key focus for the House Intelligence Committee as it conducts an impeachment inquiry looking at whether the president used his public office for private gain.