The handover of the British-led coalition base to US forces in Basra overnight was tinged with sadness, as America's senior military officer in Iraq admitted he had mixed emotions about the departure of its key ally.
"The relationship between Britain and the United States is, as your wartime leader Winston Churchill said, a 'special relationship'," said General Ray Odierno.
"Our people share a bond like no other and it has sustained us over generations as we fought against tyranny. It can still be counted on today."
Gen Odierno set the tone for a solemn occasion which paid tribute to the 179 British servicemen and women who have died in Iraq since the March 2003 US-led invasion which toppled Saddam Hussein.
"One hundred and seventy-nine gallant warriors of the United Kingdom made the supreme sacrifice," said Gen Odierno. "We have shed blood together and that is a bond that no man can break."
Lee Watson, of Britain's Royal Tank Regiment, piped in about 300 guests including military officers, diplomats and local dignitaries at the opening of the ceremony.
He played The Green Hills of Tyrol, an anthem that has accompanied British military campaigns since the Crimean War in 1853.
The guests then stood as a Royal Marines band played the Iraqi, US and British national anthems as the three flags fluttered in a light breeze and the sun came out from behind clouds that had shrouded the midday ceremony.
After Gen Odierno's tribute, the British chief of defence staff, Air Chief Marshal Sir Jock Stirrup, spoke in recognition of "those who made the ultimate sacrifice" in what he described as "a noble endeavour".
"This occasion is about the countless number of men and women from the far-flung corners of the United States and from Great Britain who have striven with such courage here in Iraq," he said.
"I salute you with pride."
General Nassir Abadi, deputy chief of staff of Iraq's armed forces, then spoke in English of his "honour" at having worked with British troops since Saddam's ouster.
"We owe a debt of gratitude that we can best repay by continuing the progress that my country has made," Gen Abadi said. "I am delighted but not surprised that the United Kingdom has stayed the course since 2003."
Gen Abadi also quoted Churchill in his tribute, saying the World War II leader had described courage as "the quality that guarantees all others ... I believe this quality has been demonstrated in abundance" by British soldiers in Iraq.
The outgoing British commander, Major General Andy Salmon, said British, American and Iraqi forces had "spilt blood together" and he had finally realised that Iraq had reached a "turning point" last October.
"The future is there for the taking," he said, referring to Iraq's January provincial elections that passed with little major violence.
He then hugged his successor, Major General Michael Oates, who said he would try to continue "the great work done by British forces" before using his final words to echo Maj-Gen Salmon's optimism.
"I see unlimited potential in southern Iraq," the US officer said.
The flag of the coalition's Multinational Division South-East, a specially-inscribed Royal Marines flag, was earlier lowered and replaced with the standard of the US Army's 10th Mountain Division.
In recognition of the multifaith gathering, a US chaplain led a prayer and wished British troops "God speed" on their journey home, before a reading from the Koran, the Muslim holy book.