Trump started Saturday at the second day of the G-7 summit in Sicily, bringing to an end a nine-day trip that started in Saudi Arabia and Israel before moving on to three European stops.
Air Force One touched down shortly before 9 p.m. EDT at Joint Base Andrews in the Maryland suburbs.
While the first half of the week saw leaders in Saudi Arabia and Israel greet Trump with open arms, Trump's arrival in Europe resurfaced questions about the US President's position toward Russian Federation and drew attention again to the federal investigation in Washington.
His body language on the trip demonstrated his typically brash behaviour, dramatised by his demands that North Atlantic Treaty Organisation allies pay more for their defence and his refusal to explicitly declare that the United States backs Article 5 of the alliance's charter, which requires each member to come to the defence of each other.
"Every single day, you protect the safety and security of the American people - and provide a symbol of hope, freedom and justice for the world", Trump said.
The president tweeted as he departed Sicily for Washington, concluding his nine-day maiden overseas trip.
"Just left the #G7Summit".
Trump has criticized Germany's trade practices before, even in person to Merkel, and suggested that he wanted to negotiate directly with German leaders to fix America's unbalanced trade with Europe's largest economy.
President Donald Trump looks at First lady Melania as he prepares to address USA military troops and their families at the Sigonella Naval Air Station, in Sigonella, Italy, Saturday, May 27, 2017.
Introduced to the stage by his wife Melania, Trump announced that his discussions during the trip had "further isolated the Iranian regime over its hostile and destabilizing actions", and stated that he "was deeply encouraged to hear from leaders of many Muslim and Arab nations that they are willing to take on a greater role in combating terrorism".
"I think we hit a home run no matter where we went", Mr. Trump said at Naval Air Station Sigonella, in Sicily.More news: Making stocks that will influence your buying rate :Halliburton Company
More news: John Wood Group PLC (WG) Price Target Cut to GBX 850
More news: French Open to start with Petra Kvitova's return to court
As their commander in chief, he noted his desire to boost military spending and promised them "my complete and unshakeable support".
But here, as during most of the public portions of his foreign trip, Trump basked in the applause and reveled in the pageantry.
While Trump emerged from the summit without a final decision on the Paris pact, he declared in a tweet Saturday that he will make a final decision next week.
"The whole discussion about climate was very hard, not to say unsatisfactory", Merkel said.
"I am so proud of the future you are going to have", he said.
President Emmanuel Macron of France said he had told Trump that it was "indispensable for the reputation of the United States and for the Americans themselves that the Americans remain committed" to the climate agreement. But Germany, for instance, has been increasing its defense spending with the goal of reaching the 2 percent target by 2024.
However, the USA president refused to commit to whether the United States would remain a part of the 2015 Paris climate-change agreement on curbing greenhouse gas emissions.
A person familiar with the negotiations at the Group of Seven summit said that six members of the G-7 would stick with their endorsement of the Paris deal, and await a decision from the U.S.
In Saudi Arabia, the first stop on the tour, Trump was at ease, admiring the king's welcome of a spectacle the actual king of Saudi Arabia had put on for him. The trip has largely gone off without a major misstep, with the administration touting the president's efforts to birth a new coalition to fight terrorism, while admonishing partners in an old alliance to pay their fair share.
Trump will now have to face developments that his son-in-law and senior adviser, Jared Kushner is under investigations for links with Russian officials.