They volunteered to serve their country. Many suffered wounds, both seen and unseen, or endured the devastating loss of comrades.
Now, veterans who were deployed in Iraq are following that country's rapid unraveling into violent chaos with a mixture of dismay and resignation. They have been left grappling with the question: What did our sacrifice achieve?
"I'm angry and extremely disappointed," said Omar Teutle, a Marine combat veteran from San Jose who served an Iraq tour in 2008. "When I was there, we made a lot of progress. Schools were built. We brought electricity and water to villages. We were protecting civilians. It's so unfortunate that it's all going down the drain."
For some vets, including those in the Bay Area, the growing anarchy also is not surprising.
"You could tell that they were slipping back into civil war," said Kevin Miller, 30, of San Francisco, who did two tours with the Marines. "The hardest part for me is thinking back on the people who didn't come home."
Iraq teeters on the precipice as deep religious divisions are ripping the country apart. The extremist group Islamic State of Iraq and Syria, consisting of Sunnis, has made stunning gains that include capturing Mosul, the second-largest city.
As the Shiite-led government struggles to restore order, President Barack Obama announced on Thursday that he is planning to send up to 300 U.S. military advisers to help retrain Iraqi security forces.
The turmoil comes less than three years after the U.S. completed the withdrawal of combat forces. And that's difficult to reconcile for Iraq veterans who see hard-fought gains lost to radical militants.
While an estimated $1.7 trillion has been spent so far in Iraq, these men and women witnessed the true cost of the war. Nearly 4,500 Americans were killed with another 32,000 wounded.
Local veterans expressed conflicted feelings about the U.S. strategy regarding Iraq -- mirroring the way American citizens long have viewed the controversial war. To some, the unfolding crisis shows the U.S. didn't finish the job, while others are left wondering whether it was inevitable. But unlike the general public, they have a deep, personal stake in that country's future.
"We're always asking ourselves: 'What was this for?' " said Richard Weir, 27, a Livermore native who served a six-month tour starting in 2008 and left the Marines as a sergeant. "I try to look at the long view, that we eventually will see the fruits of our lost blood. But that's really hard to see in the short term when things have gotten so out of control.
"It's become a mess, and it makes you wonder if it's something we can even fix."
Weir now attends the UC Berkeley School of Law and heads the school's chapter of the Iraqi Refugee Assistance Project, which assists interpreters who worked for the American military to obtain visas.
"We're getting emails from frantic clients," Weir said. "The danger has become even more imminent for them."
Peter L. Jennings, a Santa Clara University assistant professor of management, served in the first Gulf War, Iraq and Afghanistan. In late 2004, Jennings was part of the battle of Fallujah, where U.S. forces retook the city from insurgents in fighting that left 95 Americans dead and several hundred more wounded.
"I heard somebody interviewed on TV say that this was like a punch to the gut," said Jennings, 48, who was a major in both the Marines and Army. "But I might put it a little lower. It's so disheartening to see, especially knowing that it could also happen in Afghanistan when we leave there."
Jennings recalled how, after the Fallujah battle ended, Iraq held elections. He was on patrol one day when an impromptu celebration erupted as Iraqis danced and waved fingers stained with purple ink -- signifying that they had voted.
"It's not just the guys who paid with life and limbs," said Jennings, who was awarded a bronze star with valor in the Gulf War. "It's about those Iraqi people we left behind. They are suffering, too. I understand all the concerns Americans have about our involvement in Iraq. But we gave those people peace and security."
Fallujah fell back under militant control in January.
Teutle, 30, joined the Marine reserves as a way of paying back his adopted homeland after moving here from Mexico as a young boy. A staff sergeant, he deployed to Iraq for nine months in 2008 and also served two Afghanistan tours.
"We volunteered to go into harm's way," said Teutle, a San Jose State graduate student. "Our country asked us to go. Now, for us to see this happening, it's just mind-boggling. So many sacrificed so much, and it just seems like such a failure."
The crumbling of Iraq comes at a time when veterans already are enraged by the ongoing scandal involving the alleged falsifying of wait times for appointments at VA medical facilities.
The Department of Veterans Affairs has struggled mightily to keep pace with the growing needs of veterans. According to the most recent VA Health Care Utilization report, more than 1 million post-9/11 veterans already have sought out medical treatment. About 312,000 have been diagnosed with post-traumatic stress disorder.
"That's the frosting on the cake," said Teutle, of the allegations about altering wait time data. "It makes you wonder if they really don't care about the veterans."
Miller suffered internal injuries and a traumatic brain injury in an improvised bomb blast while in Iraq. Miller, like many vets, said that country's descent into violence has left him sorting through a range of emotions.
"I always had a bunch of questions," said Miller, who was a sergeant. "I never quite understood our full mission. But I served and worked hard to protect my brothers. That was the most important thing."
Follow Mark Emmons at Twitter.com/markedwinemmons.