A display of support will be given to Britain's dedicated servicemen and women today as they mark the first Armed Forces Day.
Approximately 200 community events have been organised in villages and towns around the country to honour existing service personnel and veterans.
A national event at the Historic Dockyard in Chatham, Kent is expected to host around 30,000 members of the public.
The event will be attended by Prime Minister Gordon Brown, the head of the Armed Forces, Air Chief Marshal Sir Jock Stirrup, Defence Minister Kevan Jones, and the Duke and Duchess of Gloucester.
Both the Queen and the Prince of Wales released messages today highlighting the UK's "deep and enduring gratitude" to its past and present soldiers, sailors and airmen.
The Queen will be in Edinburgh, where she will present campaign medals to the Royal Scots Dragoon Guards as the regiment's Colonel-in-Chief.
During the national event in Chatham, veterans and serving members of the Royal Navy, Army and RAF will parade through the town and into the dockyard led by the Royal Marines Band.
There will also be fly pasts by the Red Arrows and the RAF's Battle of Britain memorial flight, and a water and air display on the River Medway.
Thousands more will join major events taking place in cities, including Edinburgh, Manchester, Birmingham and Nottingham.
Mr Brown said: "One of the most humbling experiences for any Prime Minister is to meet our tremendous servicemen and women, their selfless families and those veterans whose bravery has secured our freedoms.
"We must never forget their achievements and sacrifices on our behalf in some of the most dangerous and challenging conditions - and also what they do for us in our communities at home.
"Now, through the first Armed Forces Day, we can come together to show our support and gratitude."
Armed Forces Day, which incorporates the annual Veterans Day introduced in 2006, was created following criticism that Britain did not do enough to recognise the bravery and sacrifice of its service personnel.
Many other countries, including Canada, Australia, New Zealand and the United States, already hold annual events to celebrate the contribution of their armed forces.
Sir Jock said: "The many events that are taking place today and the enthusiasm the British public has shown for Armed Forces Day mean a great deal to those in the military family. It is important for them to know that the Armed Forces are at the heart of national life, and that they enjoy the respect and appreciation of the people that they serve."
More than 3,000 Armed Forces Day flags were flown this week by councils, businesses, schools and homes from the Shetland Islands to Land's End.
The special flags were also raised by British service personnel stationed in Afghanistan, Iraq, Cyprus, Germany, Gibraltar and the Falkland Islands.
Today's events will be particularly poignant for the families of the 8,300 British troops currently serving in Afghanistan.
A total of 169 UK servicemen and women have died and many more have been wounded since operations began in the country in October 2001.
Defence Secretary Bob Ainsworth, who will be spending Armed Forces Day with troops in Afghanistan, said: "Every day, the men and women of our Armed Forces are risking their lives for the defence of our country. They are the guardians of our security and our values.
"Armed Forces Day is an opportunity for us all to recognise their commitment, their courage, and their sacrifice.
"It is also an opportunity to thank the thousands of veterans who have played so fundamental a role in protecting our country's freedom. And it is a chance to think about the families who support our brave men and women all year round."