Prince William laid a wreath at the Cenotaph in London for the first time in remembrance of the war dead on Sunday.
The young second lieutenant in the Blues and Royals regiment, second in line to the throne, followed his grandmother the Queen in paying respects to the fallen at Whitehall amid overcast skies.
Among those he remembered were his former army mentor from his training school days at Sandhurst, Major Alexis Roberts, of the Royal Gurkha Rifles, who was killed in action in Afghanistan last month.
Other royals attending included the Queen's husband Philip and children Charles, Andrew, Edward and Anne. William's brother Prince Harry, also a second lieutenant, was to attend a separate service with his own regiment.
The leaders of political parties laid wreaths, as did high commissioners of Commonwealth countries whose soldiers fought in both world wars as part of the British empire.
Thousands of veterans marched to the memorial with medals pinned to their chests, standing in silence at the Cenotaph for two minutes as Big Ben struck 11 o'clock.
Services took place around the world, including among soldiers involved in operations in Iraq and Afghanistan.
In Afghanistan, 100 Royal Marines from 40 Commando held a service in Helmand province.
More than 80 British soldiers have died in Afghanistan since the Taliban government was toppled in 2001.
The latest victim was Lance Corporal Jake Alderton who died near Sangin in southern Afghanistan last Friday when his vehicle left the road and rolled off a bridge.
His family said he wanted to be a soldier from the age of 10 and had joined an army technical college at 16.
"Like all parents who have lost a child, our lives have been shattered and life will never be the same again," his family said in a statement. "He inspired others and asked for nothing and always believed in doing the right thing."
British soldiers in Iraq also held services and parades.
About 200 veterans of the Falklands War have returned to the islands for a service of commemoration in Port Stanley.
In France, Britain's oldest war veteran, 111-year-old Henry Allingham, will lay a wreath. ( Reuters )