PARIS (AP) — United States President Joe Biden will mark the 80th anniversary of the D-Day invasion in France this week as he tries to demonstrate steadfast support for European security at a time when some allies fear Donald Trump threatens to upend American commitments if he wins another term in the White House.

The trip comes as the deadliest fighting on the continent since World War II continues in Ukraine and allied countries struggle to find ways to turn the tide against Russia, which has recently gained ground on the battlefield. It is also set against deepening cracks between the U.S. and many European allies over how to manage the ongoing Israel-Hamas war in Gaza.

Ever-dwindling numbers of World War II veterans who have pilgrimaged back to France, and Russia’s full-scale invasion of Ukraine that has dashed hopes that lives and cities wouldn’t again be laid to waste in Europe, are making the poignant anniversary of the June 6, 1944, Allied landings even more so.

The break of dawn eight decades after Allied troops waded ashore under hails of gunfire on five code-named beaches — Utah, Omaha, Gold, Juno and Sword — kicked off a day of remembrance by Allied nations now standing together again behind Ukraine — and with World War II ally Russia not invited by host France. It cited Russia’s “war of aggression against Ukraine that has intensified in recent weeks” for the snub.

Ukraine’s President Volodymyr Zelenskyy has arrived in Normandy, France, to commemorate the anniversary of the D-Day invasion with Western leaders.

Zelenskyy said on X that he is going to attend important meetings aimed at strengthening his nation at war, and that he is honored to be participating in the D-Day commemoration with President Joe Biden, French President Emmanuel Macron and others.

“This event and day serve as a reminder of the courage and determination demonstrated in the pursuit of freedom and democracy,” Zelenskyy said.