The Queen will attend the Remembrance Sunday service at the Cenotaph, leading the nation in commemorating the war dead.
The 95-year-old monarch has been under doctors’ orders to rest for almost a month.
The event will be given added poignancy by a return to pre-pandemic numbers of participating veterans and military, as well as onlookers.
The Prime Minister will be among senior politicians and members of the royal family laying a wreath at the war memorial in central London for the National Service of Remembrance.
Boris Johnson said it was a moment to “come together to remember those who sacrificed everything in service of our country”.
He said: “It’s a sacred ceremony that has endured for more than a century because we know the unpayable debt we owe those brave servicemen and women.
“We know that for our tomorrow they gave their today.
“And we know that here at home and around the world, thousands of men and women in uniform still stand ready to defend our unity and our way of life, our values, and at a cost few among us would be willing to pay”.
Labour leader Sir Keir Starmer said it was “time for us all to stop, reflect, and remember those millions of people from Britain and the Commonwealth who have kept us safe through their service and sacrifice.”
He added: “Our way of life, our values and our democracy are hard fought for through life-ending and life-changing sacrifice.
“It is that sacrifice that has ensured we can enjoy the freedoms that we live by every day and that we must never forget.”
The Remembrance service in Whitehall will return to normal this year, after the coronavirus pandemic limited the number of veterans and military and closed the ceremony to the public last year.
Hundreds of servicemen and women will line up around the Cenotaph, and nearly 10,000 veterans will march past the war memorial, watched by large crowds.
Buckingham Palace has said it was the Queen’s “firm intention” to attend the annual wreath-laying service in Whitehall.
The monarch, who lived through the Second World War as a teenager, is head of the armed forces and attaches great importance to the poignant service and to commemorating the sacrifices made by fallen servicemen and women.
It comes as she has missed several other events after being ordered to rest by royal doctors just over three weeks ago, including the Festival of Remembrance at the Royal Albert Hall on Saturday evening.
She spent a night in hospital on October 20 undergoing preliminary tests.
The Prince of Wales will lay a wreath on the top step of the Cenotaph on the Queen’s behalf as she watches from the balcony of a government building, as in previous years.
Chief of the defence staff General Sir Nick Carter said it was an “honour” to lay a wreath at the Cenotaph on behalf of “all those who have lost their lives in the service of our country”.
He said: “They died to protect the free and open way of life that we enjoy today.
“On Remembrance Sunday all members of the armed forces will reflect on this legacy, regardless of where and in what circumstances they are serving, sure in the knowledge that they now have the responsibility to uphold the values and standards that their forebears espoused.”
The Royal British Legion (RBL), the UK’s largest charity supporting the armed forces community which celebrates its centenary this year, said the march will include hundreds of young people from the Cadets, Guides and Scouts.
“It is vital the torch of Remembrance is passed to younger generations and we’re proud so many will be attending alongside veterans of all ages,” said Bob Gamble, the RBL’s assistant director for commemorative events.
He said: “For 100 years the Royal British Legion has led the nation in Remembrance to ensure the memory of those who have served and sacrificed on our behalf is upheld.
“Remembrance is part of the fabric of society, reminding us of our shared history, and today it continues to unite people of all backgrounds, communities, and generations.”
The RBL has been selling poppies, a common sight on the Western Front which became a symbol of remembrance for those killed in the First World War, in the build-up to the day as part of its annual Poppy Appeal.
A national two-minute silence will take place at 11am on Sunday to remember those who fought in past conflicts and paid the ultimate sacrifice.
Ceremonies will also take place at war memorials across the country, after being scaled back last year with the RBL advising the public to commemorate remotely by displaying a poppy in their window.
Meanwhile, members of the royal family and the Prime Minister joined a crowd of thousands to pay tribute to all those who lost their lives in conflicts at the annual Festival of Remembrance on Saturday night.
In a break with previous years, the Queen was not in attendance at the event which takes place at the Royal Albert Hall.