US President Donald Trump will join the Queen in Portsmouth to commemorate the 75th anniversary of the D-Day landings, on the final day of his UK state visit.
Theresa May will host 15 world leaders to honour the largest combined land, air and naval operation in history.
Figures from every country that fought alongside the UK will be attending.
Mr Trump said he was looking forward to going to Portsmouth to commemorate what “may have been the greatest battle ever in history”.
The countries being represented at the event have agreed to make a joint statement pledging to ensure the “unimaginable horror” of World War Two is not repeated.
Called “the D-Day proclamation”, the 16 signatories – including the UK and the United States – commit to working together to “resolve international tensions peacefully”.
The UK prime minister will use the occasion to call for continued Western unity in tackling what she will call “new and evolving security threats”.
The commemorations to mark the Allied invasion of northern France come a day after Mr Trump had a series of political meetings as part of his three-day state visit to the UK.
The president used a TV interview to play down his earlier suggestion that the NHS would be included in post-Brexit trade talks between the US and the UK.
During a joint news conference with the UK prime minister, Mr Trump had said “everything is on the table” in future discussions between the countries.
But Health Secretary Matt Hancock was among several Conservative leadership candidates who said they would not allow the NHS to become part of any trade talks.