WASHINGTON - For much of the past two decades the US military has been waging war in Iraq. And one US Army officer has been there for just about every painstaking step of it.
General Martin Dempsey has experienced first hand America's tortuous history in Iraq, from the 1991 Gulf War's swift victory to the troubled occupation after the 2003 US invasion.
As Washington's top-ranking officer, Dempsey, 62, expected to leave Iraq behind to focus on new threats. But the onslaught of the Islamic State group has drawn him - and US forces - back to Iraq again.
And the echoes of the previous war are never far away.
This month, Dempsey flew to Baghdad and found himself confronted by a problem that vexed him in the past - the country's volatile sectarian split.
After a full day of meetings, a weary-looking Dempsey said his conversations were all too familiar.
"This was like deja vu for me," he said.
After flying over the capital by helicopter, he noted the Shiite banners flying over buildings, referring to "the plethora of flags, only one of which happens to be the Iraqi flag." More than 10 years ago, Dempsey led the 1st Armored Division in Baghdad, just as Sunni-Shiite violence exploded.
Later, he was put in charge of training the Iraqi army. But the Shiite-led government's exclusion of Sunnis was a recurring frustration.
Now, as chairman of the US Joint Chiefs of Staff, Dempsey brings his sobering experience from years past to the new mission in Iraq.
And he is urging a new government led by a new prime minister, Haider al-Abadi, to make good on its promises to bridge the sectarian divide.
"I got a lot of assurances," Dempsey said. "But I made it clear that chief among our campaign assumptions is the establishment of a national unity government."
'Things fall apart'
Iraq has dominated Dempsey's career and those of a generation of American officers.
For the soldiers who served during the eight-year occupation until 2011, the Iraqi army's abject defeat at the hands of Islamic State jihadists last year was painful to watch.
"The experience was difficult when we were there," said Peter Chiarelli, a retired army four-star general who served in Iraq at the same time as Dempsey.
"But the experience has been just as difficult after we went home to watch this thing fall apart," said Chiarelli, a close friend of Dempsey's.
Chiarelli remembers the shocking bloodshed when Iraq's sectarian split erupted and his exasperation with the Shiite government led by the then prime minister, Nuri al-Maliki, who failed to reconcile the Sunni community.
In 2006, Chiarelli told decision makers that sending more US troops would merely amount to a "band aid" if Sunni-Shiite tensions were not addressed.
Nearly a decade later, Chiarelli holds a similar view about the current mission.
"We can't repeat the mistakes that we made over the last eight years," he said.
And Dempsey strikes a similar theme - suggesting the war effort will be doomed if the Baghdad government fails to make good on its vow to reach out to Sunnis.
'This is your campaign'
In this conflict, Iranian-backed Shiite militia are concentrating their firepower not on US troops but on the IS group, with a major offensive under way to recapture Tikrit.
The IS group has exploited the alienation of the Sunni population. And the Shiite militia's treatment of Sunnis already has raised alarms.
Dempsey repeatedly warned during his trip that the aftermath of the battle for Tikrit would present a high-stakes test for whether the Iraqi government could restrain Shiite fighters and deliver on its promises to Sunnis.
Dempsey's experience in Iraq came through in a letter to senators in 2013 in which he urged caution before plunging into any military action in Syria, where the IS group has also grabbed large areas of land in a brutal offensive of beheadings and forced religious conversions.
"We have learned from the past 10 years," he wrote, "that it is not enough to simply alter the balance of military power without careful consideration of what is necessary in order to preserve a functioning state." Unlike the last mission in Iraq, there is no massive American force on the ground waging a campaign against insurgents, just a small contingent of advisors and trainers.
While US warplanes pound IS extremists from the air, Iraqi troops, Kurdish militia and Shiite forces are fighting the war on the ground.
Although Dempsey has said he would be willing to ask for US forward air controllers if necessary to help direct air strikes, he and other top commanders have signaled no appetite for another large-scale commitment of troops.
At a Baghdad news conference at the end of his visit, Dempsey told Iraqi reporters this was not a war to be fought by Americans.
"This is very much your campaign - supported by us - and not our campaign supported by you."