President Trump and first lady Melania Trump arrived back in the United States early Thursday after making a surprise trip to Iraq to visit American forces stationed in the war zone.

"Just returned from visiting our troops in Iraq and Germany," the president tweeted Thursday morning. "One thing is certain, we have incredible people representing our Country - people that know how to win!"

After leaving Iraq, the president's plane stopped at Ramstein Air Force Base in Germany to refuel, giving him a second opportunity to visit U.S. troops overseas. Air Force One touched down at Joint Base Andrews in Maryland around 5:15 a.m.

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During his visit to Al Asad Air Base in western Iraq, where he thanked the troops and met with senior military leaders, Trump defended his recent announcement to pull U.S. troops out of Syria.

The planned withdrawal comes as the U.S. military has eliminated territory controlled by the Islamic State terror group in Syria and Iraq.

"I made it clear from the beginning that our mission in Syria was to strip ISIS of its military strongholds," Trump told the troops, adding that the U.S. presence in Syria was never to be "open-ended."

The unannounced trip -- Trump's first to a combat zone as commander in chief -- was shrouded in secrecy just days after the president announced the Syria troop-withdrawal plan.

"We're no longer the suckers, folks," Trump told service members at the base. "We're respected again as a nation."

The president and first lady spent about three hours on the ground in Iraq.

Trump drew criticism from some for not visiting the troops earlier in his term, which is nearing the halfway point. But in a November interview with Chris Wallace on "Fox News Sunday," he said he had plans to make a visit troops abroad.

"Well, I think you will see that happen," the president said after Wallace noted that former presidents Barack Obama and George W. Bush had each visited service members in war zones. "There are things that are being planned. We don’t want to talk about it because of — obviously because of security reasons and everything else."

Trump's visit angered some Iraqi officials, with two major parties in the country's parliament condemning the visit.

Trump campaigned in part on removing U.S. troops from troubled spots such as Syria, Iraq and Afghanistan. The Pentagon is possibly working on a plan to withdraw nearly half of the 14,000 troops still serving in Afghanistan.

The Associated Press contributed to this report.