US president Donald Trump returns to Europe this week and will have his first encounter with Russian president Vladimir Putin.
Mr Trump's first visit to the continent in May stirred anxieties among European allies when he declined to endorse Nato's common defence treaty explicitly and scolded world leaders for not spending more on their armed forces.
This time, Mr Trump will use stops in Poland and Germany to try to pull off the tricky balancing act of improving ties with Moscow at a time of particularly fraught relations while also presenting the US as a check against Russian aggression.
Mr Trump is leaving Washington for Europe on Wednesday. In what may be the most-watched event of the four-day trip, the president will meet Mr Putin on Friday on the sidelines of an international summit in Hamburg, Germany.
Every aspect of the meeting between the two unpredictable leaders is sure to be closely scrutinised as investigations press on into alleged Moscow meddling in the 2016 election and potential Trump campaign collusion.
With those investigations hanging in the air, there is little expectation the meeting will produce significant progress on difficult issues such as the crisis in Ukraine or the conflict in Syria.
"I can't imagine any issue they can actually make major headway on, given the poison that surrounds the relationship," said Michael O'Hanlon, a senior fellow in foreign policy at The Brookings Institution, who suggested it might lay the groundwork for future cooperation.
The Trump-Putin encounter will be one of at least nine meetings the US president will have with foreign leaders while in Hamburg for a G-20 summit of industrial and emerging market nations, beginning on Friday.
But first Mr Trump will stop in Poland, where leaders are looking for reassurance that the presence of US and Nato troops there will continue as long as the region's security is threatened by a resurgent Russia.
In return, Mr Trump will be expecting a warm reception as he pays homage to Polish resolve with a speech in Krasinski Square, his first major outdoor address in a foreign country.
Poland's leaders are closely aligned with Mr Trump's worldview, and ruling party politicians and pro-government activists plan to bus in groups to help ensure an enthusiastic crowd for the president.
Previewing the trip, White House officials said Mr Trump would reiterate the US commitment to Nato's Article 5, which says an attack on one member is an attack on all - something he did not do at Nato headquarters in Brussels during his first overseas trip but eventually endorsed last month. The president is also expected to cite the need to develop "a common approach to Russia," his advisers said.
"He'd like the United States and the entire west to develop a more constructive relationship with Russia," said the White House national security adviser, HR McMaster. "But he's also made clear that we will do what is necessary to confront Russia's destabilising behaviour."
Preparing for the trip, Mr Trump spoke on Monday with German Chancellor Angela Merkel and Italian Prime Minister Paolo Gentiloni. Earlier in the holiday weekend, he had conversations with Chinese President Xi Jinping, Japanese Prime Minister Shinzo Abe and the leaders of Saudi Arabia, the United Arab Emirates and Qatar.
After this trip, the president will be back in Europe soon for a mid-July visit to France to celebrate Bastille Day alongside new French President Emmanuel Macron. And in late July, he will send US vice-president Mike Pence to Estonia and Georgia - two former Soviet satellites straddling the Russian border - and new Nato member Montenegro.
