Armed forces personnel have set off on a 1,000-mile "March for Honour" to raise £1m for the Royal British Legion.
The Army, Royal Navy, Royal Air Force and Royal Marines teams started from various places in the UK.
Royal Navy team captain, Chief Petty Officer Jan Matthews, said the march honoured those killed in conflict.
The team members, each carrying 40lb of kit, will then head to London's Royal Albert Hall together in time for Remembrance Day on Thursday.
Each team aims to walk up to 250 miles of the 1,000 miles and will all pass through Wootton Bassett, Wilts, on Tuesday.
The Royal Navy team set off from HMS Victory in Portsmouth Historic Dockyard, the Royal Marines started at Plymouth Hoe, and the RAF set off from the war memorial in Stamford, Lincolnshire.
The Army departed from Cardiff Castle.
They decided to meet at Wootton Basset because it is the town where those killed in Afghanistan are traditionally honoured in a parade when their bodies are repatriated.
The teams will each deliver a Book of Remembrance to the Royal Albert Hall on Remembrance Day.
The Royal Marines began the challenge by abseiling from Sea King helicopters into Plymouth Hoe before holding a short memorial service.
CPO Matthews, a physical training instructor, said: "When I was asked to take part in March For Honour I was delighted.
"The march provides an opportunity to pay tribute to those who have given their life in conflict and also raise funds for the vital work of the Royal British Legion."
Sean Power, one of the team of five, said they aimed to cover 47 miles across Dartmoor on the first day.
"It's going to be very gruelling. The challenge is going to be mentally tough as well as physically tough," the 28-year-old told the BBC.
"But that's nothing compared to what the lads are going through out in theatre. The goal of the challenge is worth the effort you put in."
As a Royal Marine, he saw active service in Iraq and Afghanistan, but left in 2008 to pursue a career as a photojournalist and is now a reservist.
He hopes to return to the battlefront when he has qualified from his college course as a photojournalist.
He said he wanted to give something back to the Legion after it gave him £5,000 to replace his photographic equipment when it was stolen in a burglary at his London home.
"I've got a friend who lost both his legs and the Legion paid for the redesign of his house to make it wheelchair friendly. They do an amazing job every day," he said.
March for Honour was devised by L/Cpl Ram Patten, who was helped by the Legion after suffering post-traumatic stress disorder following a tour of Afghanistan.
He said he had struggled to re-adjust to everyday life in the UK and needed nine months of therapy at a mental health clinic with regular weekly sessions.
Prime Minister David Cameron invited him to Downing Street last month to support the fund-raising project.
Funds from March For Honour and the 2010 Poppy Appeal will pay for welfare and rehabilitation work for the armed forces community.
Since 2003, the Royal British Legion has helped 10,000 serving and ex-serving members and their families who are part of the Iraq and Afghanistan generation.