The Queen led the nation in honouring members of the armed forces killed in conflict as Remembrance Sunday services took place around the country and in a former war zone today.
Prince Harry travelled to Afghanistan to pay an emotional tribute to fallen comrades in the country he last served in January 2013.
The prince left a personal wreath at Kandahar airfield inscribed with the handwritten note: "There is no greater love than to lay down one's life for one's friends. They will never be forgotten. Harry."
Back in England, the Queen laid the first wreath at the Cenotaph in London's Whitehall to commemorate those who have made the ultimate sacrifice in the decades since the First World War.
Senior royals, including Second World War veteran the Duke of Edinburgh, the Prince of Wales and the Duke of Cambridge joined politicians, military leaders, veterans and serving personnel in laying wreaths of poppies at the monument.
Elsewhere, thousands fell silent at the Tower of London, where the field of ceramic poppies has proved so popular that the Government announced a part of the artwork will go on display at the Imperial War Museum after a national tour.
Prime Minister David Cameron described this year's Remembrance Sunday as "particularly poignant" as 2014 marked the 100th anniversary of the start of the First World War, the 70th anniversary of the D-Day landings and the end of Britain's 13-year conflict in Afghanistan.
Millions across the UK fell silent in tribute to those lost in war, joining the crowds gathered in central London who stood in a moment of quiet contemplation as Big Ben struck 11am.
Amid heightened fears of a terror attack, there was a large police presence at the Cenotaph in Whitehall, with armed officers on patrol and a helicopter hovering above the site before the ceremony.
Scotland Yard said it had an "appropriate and proportionate" policing plan in place for the event, after four men were arrested in connection with an alleged Islamist terror plot on British soil on Thursday.
At the heart of the service was a two-minute silence, marked at the beginning and end by the firing of a round by the King's Troop Royal Horse Artillery, using a 13-pounder First World War gun.
Buglers of the Royal Marines then sounded the Last Post at the end of the silence.
In cool and overcast conditions, the royals and dignitaries laid their wreaths at the Cenotaph.
Mr Cameron was first after the royals to do so, followed by Deputy Prime Minister Nick Clegg and Labour leader Ed Miliband. Former prime ministers Sir John Major, Tony Blair and London mayor Boris Johnson also took part in the ceremony.
The Duchess of Cambridge and Duchess of Cornwall watched from the Foreign Office balcony.
Shortly after the two-minute silence, a young choir boy collapsed at the Cenotaph yards from where the royal family were standing.
As the national anthem was sung, medics rushed to treat the boy who was helped up and led away through the crowd.
The Queen, who wore a long black coat and hat and carried a black handbag during the service, was met by spontaneous applause which spread through the crowds as she left the Cenotaph.
Forty-six high commissioners from Commonwealth countries each laid a wreath before the Irish ambassador to the UK, Dan Mulhall, left a floral tribute.
It was the first time a diplomat from the Irish Republic has laid a laurel wreath at the London Cenotaph - the latest in a line of symbolic gestures by both the UK and Ireland aimed at putting their troubled history behind them.
Following the service, more than 10,000 veterans marched past the Cenotaph, before the Duke of York took the salute at Horse Guards Parade.
Dressed in their traditional attire of suits and bowler hats with furled umbrellas, the Prince of Wales later joined the Welsh Guards Association for their march to Horse Guards Parade, where he took the salute before laying a wreath.
Since the last Remembrance Sunday, seven British forces personnel have died on operations.
Speaking near the Cenotaph, Company Sergeant Major Paul Baines, 39, from Torquay, who was awarded the military cross for gallantry after serving in Afghanistan, said: "The country has really rallied behind the military and not just because of the centenary year.
"When I was younger I tried to imagine the faces of those who had lost their lives.
"When you experience it for yourself as part of your job, it becomes more personal."
Company Sergeant Major Baines, who served with the 1st Battalion Coldstream Guards, said his thoughts were particularly with five of his colleagues killed on his last tour of Afghanistan, as well as 10 soldiers who had limbs amputated.
They included Acting Sergeant John Amer, who became the 99th British casualty in Afghanistan in 2009 after he died from wounds suffered in an explosion in central Helmand Province.
"I woke up in the bed next to his and that day he was killed," he said. "I don't feel lucky. I appreciate the sacrifices taken when we were out there."
Sergeant Anna Irwin, 35, a Chinook helicopter crewman based at RAF Odiham in Hampshire, who completed eight tours of Afghanistan, said: "It definitely stirs up emotions. It's a time to reflect and think about those who have given up things for us to have our freedom."
Joan De Vall, 89, and 87-year-old Anne Atkinson completed the Remembrance Sunday march in London after serving with the Auxiliary Territorial Service during the Second World War.
Speaking of her military service, Ms De Vall, from Aylestone in Leicestershire, said: "It was a wonderful time. You don't tend to remember the bad times.
"I always love these days, to see so many people you may not see again for a long time."