US President Donald Trump will on Sunday attend sombre commemorations in Warsaw of the outbreak of World War II, 80 years ago.
Trump will be the first US head of state to visit Poland to mark the anniversary of the start of the war, which claimed 50 million lives, including those of six million Jews in the Holocaust.
Few other major leaders are expected in the Polish capital, as French President Emmanuel Macron and German Chancellor Angela Merkel are not coming, while Russian President Vladimir Putin was not invited.
According to the Polish presidency, around 40 foreign delegations are expected, half of them led by heads of state.
They include Ukrainian President Volodymyr Zelensky, whose partnership is important to Poland, which believes its security depends on Ukraine remaining outside of Russia's sphere of influence.
Warsaw said Putin was snubbed this time - unlike 10 years ago - because of Moscow's 2014 annexation of Crimea from Ukraine.
"It would be inappropriate to commemorate the anniversary of armed aggression against Poland with the participation of a leader who is today acting this way towards a neighbour," Poland's deputy prime minister Jacek Sasin said in July.
Russia's foreign ministry responded with "bewilderment", noting Moscow's "unquestionably decisive contribution to the defeat of Hitler's Reich".
First bombs at dawn
On August 23, 1939, Germany and the Soviet Union secretly agreed to carve up Eastern Europe between them by signing the Molotov-Ribbentrop Pact.
The World War II began a week later on September 1 when a Nazi German battleship opened fire on a Polish fort in Westerplatte in the Baltic Sea. That same morning the Nazis also bombed the central city of Wielun.
At dawn on Sunday, Polish President Andrzej Duda and his German counterpart Frank-Walter Steinmeier will attend a remembrance service in Wielun.
Polish Prime Minister Mateusz Morawiecki and European Commission Vice-President Frans Timmermans will take part in a ceremony in Westerplatte, a peninsula of the port city of Gdansk.
There will then be a series of speeches in Warsaw's Pilsudski Square, the site of the Tomb of the Unknown Soldier.
Poland suffered some of the worst horrors of the war: nearly six million Poles - half of them Jews - died in the conflict.
Hitler's attack on Poland led the UK and France to declare war on Nazi Germany. On September 17, the Soviet Union, in turn, invaded Poland.
After the Nazis tore up the pact with Moscow, two alliances battled it out to the end: the Axis powers led by Germany, Italy and Japan and the victorious Allied forces led by the UK, the Soviet Union and the United States.
Friction with EU
Trump's trip to Warsaw is a sign of warm ties between Washington and Warsaw at a time when both countries are at loggerheads with the European Union.
Trump, who has been openly hostile to the EU, sparring with Brussels on issues including trade and Iran's nuclear ambitions.
And Poland's right-wing government has run afoul of the EU for logging in one of Europe's last primaeval forests and introducing judicial reforms that Brussels calls a threat to the rule of law.
"As the Polish government has been finding itself in difficulty with the EU, it's been strengthening its efforts to be closer with the US. And that is in a sense being reciprocated," said political analyst Marcin Zaborowski.
"Trump likes people who like him, and the current Polish leadership adores him. By the same token, the Polish government appreciates the impression that it is treated as a close partner by the most powerful country in the world ... Chumming up with Trump dispels the impression of international isolation," he told the AFP news agency.
Trump was originally set to travel on to Denmark after Poland, but he postponed the trip after Copenhagen rejected his idea of purchasing its autonomous territory Greenland.
Around 5,000 US soldiers are deployed along with NATO forces in Poland as a counter against possible Russian action.
Trump announced in June that he would send 1,000 more troops, a decision he is expected to affirm during his visit.
Additionally, "the US wants to seal deals on arms sales to Poland", including F-35 fighter jets, Zaborowski said.
The Polish presidency said cooperation accords in defence and energy were also in the offing.
One point of contention that could come up is the restitution of Jewish properties seized during the Holocaust.
US Secretary of State Mike Pompeo urged Poland to "resolve" the issue through legislation during a visit to Warsaw in February.
But Warsaw insists the matter is closed, saying a 2017 US law requiring State Department monitoring of Poland's progress on the issue will have no impact at home.