UK Prime Minister Tony Blair has told British troops in Iraq that they took part in "a momentous and mighty act" in liberating the country from Saddam Hussein.
British troops 'have brought tremendous honour on our country'
Mr Blair said history would look back on the Iraq conflict as "one of the defining moments of the century".
The prime minister, who met troops at two bases in southern Iraq, is the first Western leader to visit the country since Saddam's regime was toppled.
After the trip he flew to Poland to switch from marking the coalition victory to healing the international rift it has
He will embark on a round of meetings with dozens of
world leaders which will end in Evian, France, with the G8 summit before he returns home to London next Tuesday.
During his visit to Iraq, Mr Blair visited a school and held talks with British and Iraqi officials.
Addressing 400 British troops outside one of Saddam's former presidential palaces in Basra, he said: "I would just like to express the sense of pride that everybody has in Britain at the magnificent job you have done.
"I know there were a lot of disagreements in the country about the wisdom of my decision to order the action.
"But I can assure you of one thing - there is absolutely no dispute in Britain at all about your professionalism and your courage and your dedication and not just in the way you won the war, which was extraordinary, but the way you are conducting the peace, which is remarkable."
Mr Blair said the taking by UK troops of the al-Faw peninsula and Basra "and the way it was done with the minimum loss of civilian life is famous right round the world now".
Speaking of those who lost their lives in the conflict, he said: "There were people you will have known who aren't going back home and we grieve for them and we pay respect to them for everything they did and the sacrifice they made."
The prime minister's speech was welcomed by soldiers, including Bombardier Hazel Savage, from Nottingham, who said: "It shows us what he thinks and what people in England really think. It was great."
Her colleague Marc Rylance, from Liverpool, added: "It was positive and shows people are supporting us even if we haven't been able to see it over on this side very much."
Earlier Iraqi children clapped and performed nursery rhymes as Mr Blair met teachers and toured classrooms and a playground at a school in Basra.
The prime minister had travelled in the cockpit of the RAF Hercules C130 plane which flew him from Kuwait into Iraq for the historic visit.
Before returning to Kuwait City, he visited Umm Qasr to meet the British troops who captured and held Iraq's only sea port.
But the six-hour visit has been overshadowed by controversy about the likelihood of weapons of mass destruction being found.
Mr Blair made Saddam's weapons programmes a central part of his case for taking action against Iraq.
But US Defence Secretary Donald Rumsfeld has suggested that the weapons might have been destroyed before the fighting began.
And on Thursday, doubts were raised about the dossier of evidence the UK Government presented against Iraq last September.
A senior British intelligence official told the BBC the original version of the document had added little to what was already publicly known, but that a week before it was published it had been "transformed" on the orders of Downing Street.
Abbas Adnan greeted Mr Blair with kisses
The aim was to make the report more hard-hitting, the official told the BBC, adding that the intelligence services were unhappy about the changes.
But Downing Street denied the claims, saying: "Not one word of the dossier was not entirely the work of the intelligence agencies."
Mr Blair has said he is still absolutely sure that weapons of mass destruction will be found.
While in Iraq, he also met John Sawers, the UK's new representative in Iraq, along with Paul "Jerry" Bremer, the head of America's Office of Reconstruction and Humanitarian Assistance.
Meanwhile, the prime minister's newly appointed special envoy on human rights in Iraq, Labour MP Ann Clwyd, is in Baghdad as she starts work in the role.