Former Prime Minister Tony Blair is to donate the profits from his memoirs to a sports centre for badly injured soldiers.
A spokesman said Mr Blair would hand over the reported £4.6m advance payment plus all royalties to honour "their courage and sacrifice".
The Royal British Legion will receive the money after the book, called A Journey, is published next month.
This would make a "lasting difference" to injured personnel, it said.
The money will go the Legion's £25m Battle Back Challenge Centre, which is due to open in summer 2012.
A spokesman for the former prime minister said: "In making this decision, Tony Blair recognises the courage and sacrifice the armed forces demonstrate day in, day out.
"As prime minister he witnessed that for himself in Iraq, Afghanistan, Northern Ireland, Sierra Leone and Kosovo. This is his way of honouring their courage and sacrifice."
He said that after consulting with numerous people, there was "one project consistently highlighted: The Royal British Legion's Battle Back Challenge Centre."
"As Tony Blair said to the House of Commons on his last day in office: 'I believe that they [the Armed Forces] are fighting for the security of this country and the wider world against people who would destroy our way of life. But whatever view people take of my decisions, I think that there is only one view to take of them: they are the bravest and the best.'"
Peter Brierley, whose son Lance Corporal Shaun Brierley was killed in Iraq 2003, said the donation would be welcomed by the British Legion but it was "blood money".
He said Mr Blair had made an "absolute fortune" from his decision to go to war, through speaking engagements in the US after stepping down as prime minister.
Mr Brierley told the BBC News Channel: "This gift, or donation, is an absolutely fantastic thing, but it doesn't alter my aim that one day we will see Tony Blair in court for the crimes he committed."
Mr Blair's former communications adviser Lance Price said the former prime minister would "have faced a lot of criticism if he had just pocketed the money" as he was now "a very wealthy man".
Mr Blair's friend and former constituency agent John Burton said: "He wouldn't do it out of a guilty conscience because he is quite convinced the reasons for going into Iraq are still right."
Mr Blair, who is currently out of the UK, is not expected to comment on the gift.
He is reported to have earned more than £12m since leaving office in 2007 with a string of directorships, including insurance giant Zurich and investment bank JP Morgan, speaking engagements and business consultancies.
'Unflinching' detail
He is also an unpaid Middle East peace envoy for the "Quartet" made up of the United Nations, the European Union, the US and Russia.
Mr Blair's publisher Random House has promised the book will provide "frank, unflinching" detail of his time in office, including his relationship with Gordon Brown.
Key figures from Mr Blair's 13 years in power, including Alastair Campbell, Lord Mandelson, Lord Prescott and Mr Blair's wife Cherie, have already published their own accounts of his time in Downing Street and the rise of New Labour.
Senior Labour figures, including Mr Blair, were reported to be upset about Lord Mandelson's book, The Third Man, which laid bare the bitter infighting at the heart of New Labour.
The former business secretary is reported to have been paid £400,000 for the serialisation rights alone.
Mr Blair's successor as prime minister, Gordon Brown, is currently writing a book on the financial crisis which is due to be published later this year.
Chris Simpkins, director general of the Royal British Legion, said: "Mr Blair's generosity is much appreciated and will help us to make a real and lasting difference to the lives of hundreds of injured personnel."
Mr Blair's predecessors as prime minister Sir John Major and Lady Thatcher also wrote memoirs after leaving office.
