Millions of people across the UK are expected to observe a two-minute silence later to mark Armistice Day.
The annual event starts at 11:00 GMT, mirroring the time guns along the western front fell silent for a final time at the end of World War I in 1918.
Ceremonies will commemorate those who died in two world wars and later conflicts, including 385 UK personnel killed in Afghanistan since 2001.
In London, a ceremony will take place at the Cenotaph in Whitehall.
Chief of the Defence Staff, General Sir David Richards, and the professional head of the Army, General Sir Peter Wall, will attend along with servicemen and women.
The Royal British Legion – which is celebrating its 90th anniversary this year – is also holding a “Silence in the Square” event in Trafalgar Square.
There will be readings and performances in the run up to the silence from Downton Abbey actor Dan Stevens, Strictly Come Dancing’s Vincent Simone and Flavia Cacace, and singing trio The Soldiers.
Events are planned across the UK including in Glasgow, Cardiff, Belfast, Plymouth and Newcastle.
Further afield, the Commonwealth War Graves Commission will be holding services at its cemeteries in Libya in Tripoli, Benghazi and Tobruk.
British service personnel in Afghanistan held a two-minute silence at 11:00 local time (06:30 GMT).
Three thousand troops at the main British base in Afghanistan, Camp Bastion in Helmand province, took part in a ceremony attended by Defence Secretary Phillip Hammond, making his first visit to the country since his appointment last month.
The joint force senior chaplain at Camp Bastion, Padre Cole Maynard, said the fallen of conflicts past and present had been remembered.
He said: “As they stand here they’re remembering their friends who died. Sadly, some of them would have died this summer. Some of them would have died last summer. And some of them would have died 10 years ago.
“So it’s a very moving occasion that brings the past – and honouring the dead of the past – right up to honouring the dead of only these last few days.”
Mr Hammond, who arrived in Kabul on Wednesday, has already been to Lashkar Gah and accompanied troops from the 3rd Battalion the Royal Regiment of Scotland on a foot patrol in Nad-e Ali.
The defence secretary, who has been to the hospital at Camp Bastion, said he was incredibly impressed by the troops’ professionalism in the face of “very real danger”.
“There’s a constant stream of battlefield casualties coming through the hospital, and these people know that they’re living with that risk, day in and day out.
“And yet they manage coolly, professionally and in an absolutely calm way. So we’re immensely proud of them. They can be immensely proud of themselves,” he said.
Ceremonies at sea
The 93rd Armistice Day will be commemorated by other members of the British armed forces, wherever they are – be it Cyprus or onboard Royal Navy vessels at sea.
In Staffordshire later, a service of remembrance will be held within the walls of the Armed Forces Memorial at the National Memorial Arboretum.
According to the arboretum, the memorial is designed so that on the 11th hour of the 11th day of the 11th month, a shaft of sunlight shines through its inner and outer walls, hitting the central bronze wreath sculpture.
On Thursday evening, the Duke and Duchess of Cambridge held a fundraising dinner at St James’ Palace in aid of the memorial’s £12m appeal to build further facilities for visitors.
Prince William launched the appeal and became its patron when he visited the arboretum in April 2009.
In a speech, he said it had become the focal point for the nation’s remembrance.
“Those who make the journey to visit the National Memorial Arboretum – whether they are the families of those commemorated, old comrades, or simply those who wish to acknowledge the debt owed and to learn – deserve to be looked after when they are there,” he said.
“That is why this appeal was launched.”
The Archbishop of Canterbury will visit the Royal Naval Air Station at Yeovilton, Somerset, to take part in the Act of Remembrance at the Royal Naval Cemetery at St Bartholomew’s Church.
Traffic will be stopped in Inverness city centre for the two-minute silence – the first time since World War II that this has happened.
Leicester Cathedral clock has undergone last-minute repairs to enable it to time the start of the silence. It had stopped working following the theft of copper wiring last month.
Events at the Cenotaph and other public locations will be broadcast on BBC Two and on the BBC News Channel.
The National Service of Remembrance, led by the Queen, will take place at the Cenotaph on Sunday.