The Prince of Wales will urge nations to stand up against intolerance and strive for a “better tomorrow” during a remembrance ceremony in Germany.
In a speech on Sunday, Prince Charles will also call on the UK and Germany to “reaffirm” their bond as they “begin this new chapter in our long history”.
His wife, Camilla, is joining him on their first official overseas visit since the start of the Covid pandemic.
It comes as post-Brexit trade talks are reaching their crucial final stages.
The prince will also say the global crises of the pandemic and climate change “demand” that the the UK and Germany “act together”.
Prince Charles and the Duchess of Cornwall flew to Berlin Brandenburg Airport on Saturday evening in the UK’s ministerial RAF Voyager jet – the first time it has flown dignitaries since a makeover costing almost £1m.
The prince, who celebrated his 72nd birthday on Saturday, was presented with a birthday cake during the flight.
Prince Charles and the Duchess of Cornwall will be the first members of the Royal Family to attend the ceremony at the German parliament in Berlin, marking the country’s National Day of Mourning for victims of war.
The speech comes 75 years after the end of World War Two and will highlight the friendship between the two nations.
The prince is expected to say: “We must be resolute in addressing acts of unspeakable cruelty against people for reasons of their religion, their race or their beliefs, wherever they occur in the world.
“We must stand alongside each other in determined defence of the future we owe our children and our grandchildren.”
He will add: “We are heavily invested in each other’s futures, such that our national interests, whilst distinct, will always be entwined…
“Let us reflect on all that we have been through together, and all that we have learned. Let us remember all victims of war, tyranny and persecution; those who laid down their lives for the freedoms we cherish, and those who struggle for these freedoms to this day.”
The Royal Family have carried out a number of European visits since the UK voted to leave the EU in 2016.
During a tour of Germany in May last year, Prince Charles said the bonds between the UK and Germany “will, and must endure” post-Brexit.
And when his son, the Duke of Cambridge, visited the country in 2016, William said the depth of Britain’s friendship with Germany would not change after the UK left the EU.
Ahead of his trip, the Prince Charles held a telephone meeting with German Chancellor Angela Merkel.
A statement from Clarence House said Prince Charles and Camilla had been invited to Germany by President Frank-Walter Steinmeier, and they would also attend a wreath-laying ceremony at the Neue Wache Memorial.
It said the National Day of Mourning would this year focus on “German-British friendship”.
“The event pays tribute to the Allied commitment to the liberation from Nazi occupation and to the reconstruction, re-democratisation and subsequent reunification of Germany. It remembers all victims of war and tyranny,” the statement added.