Correction: An earlier version of this story incorrectly stated the year the United States initiated its troops “surge” in that country. It was 2007, not 2009. 
 
 The towering former three-star general keeps a wooden box on his desk with the photos of 257 service members who died in Iraq under his command, sorted by date. During quiet moments, usually a couple of times a week, Mark Hertling opens the lid, inscribed with the words “Make it Matter,” flips through the laminated portraits of uniformed troops and reflects on their loss. 
 
 “I try to keep track of anniversaries of the deaths and say a prayer for them and their families,” said Hertling, who now works at a hospital in Orlando. “During the holiday season, you think about the young men and women killed in 2003, 2004 and figure they would have been in their 30s now, with a couple of kids.” 
 
 The ritual was never easy. It has become increasingly painful over the past two years, as Hertling and a generation of troops and civilians indelibly shaped by harrowing tours in Iraq have watched the country unravel from afar. 
 
 The Iraq war may have never been declared lost. But the stunning surge in violence over the past year — and the return of al-Qaeda in the western province of Anbar this month — is forcing Americans who invested personally in the war’s success to grapple with haunting questions. 
 
 “Could someone smart convince me that the black flag of al-Qaeda flying over Fallujah isn’t analogous to the fall of Saigon?” former Army captain Matt Gallagher asked on Twitter. “Because. Well.” 
 
 Gallagher, 30, who left the Army to pursue a writing career in New York, has kept close tabs on Iraq since the end of his deployment as a platoon commander in the outskirts of Baghdad in 2009. He has a Google alert for Saba al-Bor, a small village northwest of Baghdad where his infantry platoon spent 15 months living in terror of armor-penetrating roadside bombs and in awe of the complexities of tribal politics. 
 
 Gallagher, who was part of the troop surge ordered by the George W. Bush administration, felt his stomach churn a couple of months ago when an alert prompted him to click on a video of a suicide bombing in his old battleground. He had the same reaction watching grainy footage of masked al-Qaeda militants raising the black flag of jihad in Fallujah. 
 
 He said he has gradually come to accept that the sustained peace he and fellow soldiers had fought for has not lasted. 
 
 “It’s a very disconcerting and ugly thing to reconcile as an individual,” said Gallagher, who kept a vivid and popular blog during his deployment. 
 
 This week, muddled accounts of fighting between al-Qaeda militants, tribesmen and Iraqi troops thrust Iraq back into the headlines. At Camp Lejeune, N.C., a 30-year-old Marine staff sergeant who served tours in Fallujah and Ramadi found himself seething. He thought about his mind-set on his first deployment, when he was fresh out of basic training. 
 
 “I was terrified half the time,” said Paul, who asked to be quoted only by his first name because he now serves in a Special Operations regiment. “The way my 20-year-old self envisioned it, I was fighting evil in the world, in a place where people are being treated terrible and getting murdered and have zero rights.” 
 
 In hindsight, that idealism seems absurd, and the memories painful. 
 
 “It brings back a lot of anger,” Paul said. “I feel like it’s been a big waste of time. It’s kind of like, why the hell did all my buddies die there for? There’s no purpose to it.” 
 
 This week, Gen. Ray Odierno, the head of the Army and one of the architects of the 2007 troop surge he and others came to see as a strategic success, was asked whether the United States should consider deploying troops to Iraq once again. No, he said. The general called the situation in Iraq disappointing, summing it up using language that commanders used in the past to explain what Americans fought and died to avoid over a decade of war. 
 
 “The big threat to our national security is ungoverned territory, areas where we have terrorist organizations that become dominant and then try to export their terrorism outside the Middle East and into several other countries, including the United States,” he said at a National Press Club luncheon Tuesday. 
 
 Odierno’s longtime political adviser in Iraq, an Arabic­speaking Briton who now teaches Middle East politics at Yale University, was speechless when she caught a glimpse of news footage of Anbar while working out recently. Emma Sky has long considered the Iraq war lost, but the sight was bloodcurdling. 
 
 “It brought back memories of Iraq’s darkest days, which we all hoped had been left behind,” she said. “So many U.S. soldiers put their lives and souls into giving Iraqis hope for a better future than they had under Saddam.” 
 
 America’s role in the Iraq war ended with little fanfare. Months before the last troops crossed the border into Kuwait, the U.S. military began calling the mission there Operation New Dawn. Commanders portrayed American troops as advisers and enablers, rather than combatants, and said the war was now for the Iraqis to win or lose. 
 
 There were no victory parades or symbolic displays of jubilation to mark the end of an awful conflict from which 4,486 American troops returned in coffins. A couple of months after the pullout, President Obama hosted Iraq veterans at the White House to honor their service. Vice President Biden declared to those in attendance: “You adapted, you succeeded and you defeated.” Then Obama, dressed in a tuxedo, took to the podium, flanked by a golden curtain. 
 
 “In one of our nation’s longest wars, you wrote one of the most extraordinary chapters in American military history,” the commander in chief said. “Now the Iraqi people have a chance to forge their own destiny, and every one of you who served there can take pride in knowing you gave the Iraqis this opportunity; that you succeeded in your mission.” 
 
 To many veterans, those words now ring hollow. 
 
 They don’t entirely to Hertling, who continues to hope that Iraq will somehow pull through. But he’ll always be troubled by the toll the conflict took on his family. Hertling, his two sons and a daughter-in-law spent a total of 12 years deployed in Iraq. Each son lost a soldier in his platoon, deaths that scarred them for life, he said. The Hertlings have been wrestling this week with the question of what it was all for. 
 
 “You bounce back and forth between: Was it a complete failure, or did we do the best we could and handed it over to them when things were relatively calm?” he said. “Every person who served in Iraq or Afghanistan never loses that part of them when they come home. It becomes part of their soul.” ||||| But Islamic State of Iraq and Syria fighters still appeared to have the upper hand, witnesses and others reached by telephone said, and there was no question that the group had scored a propaganda victory against Mr. Maliki, whose authority over Anbar Province has been severely undermined in the two years since American forces left the country. 
 
 The group’s fighters cut power lines in Falluja late in the day and ordered residents not to use their backup generators. In one area of Falluja, a militant said over a mosque loudspeaker: “We are God’s rule on Earth! No one can defeat God’s will!” 
 
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 The group advanced hours after a short period of calm had returned to the city, where the traffic police and street cleaners resumed work during the day and mosque loudspeakers exhorted stores to reopen so hungry residents could buy food. 
 
 The calm evaporated when the militants appeared at the close of Friday Prayer — which had been moved by local imams to a public park, away from the combat zones — and seized the stage, waving the Qaeda flag and daring the authorities to evict them. 
 
 “We declare Falluja as an Islamic state, and we call on you to be on our side!” one fighter shouted to the crowd, according to witness accounts. 
 
 Referring to Mr. Maliki’s government and its Shiite ally Iran, the fighter shouted, “We are here to defend you from the army of Maliki and the Iranian Safavids!” The Safavid dynasty ruled present-day Iran and Iraq hundreds of years ago. 
 
 The resumed fighting included other areas of Anbar Province, including its largest city, Ramadi. 
 
 It has pitted Qaeda-affiliated Sunni extremists, who now control large amounts of territory in the desert province, against the forces of the Shiite-dominated central government, backed by local tribesmen who are not strong supporters of the government but, in this struggle, have decided to side with the army and the police against Al Qaeda. 
 
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 The fight has become a severe test of Mr. Maliki’s ability to hold the country together. 
 
 The combat scenes in Anbar, which was the heart of the Sunni insurgency during the American occupation and was where more than 1,300 American soldiers were killed, have provided the sharpest evidence yet of a country descending into a maelstrom of violence. 
 
 For the Qaeda militants in Iraq, who are fighting under the same name as the most extremist Sunni rebels in Syria, the gains they have made in Anbar appear to be a significant step toward realizing the long-held goal of transforming Iraq and Syria into one battlefield for the same cause: establishing a Sunni Islamist state. 
 
 Falluja and Ramadi Falluja and Ramadi were major battlegrounds during the war in Iraq. Both towns formed focal points of the armed Sunni Arab insurgency against the American-led military presence. In 2004, Falluja was the site of one of the biggest battles of the war as international forces struggled to wrest it from insurgent control. Dozens of allied soldiers were killed and hundreds wounded over eight days of sustained street-to-street combat. Ramadi was also rocked by regular insurgent violence. In 2006, American officials recorded as many as 25 violent episodes every day in Ramadi. Violence in both towns was largely tamed in 2007 when groups of local Sunni Arab leaders, some former militants themselves, organized into “Awakening Councils” that worked with American forces to turn their communities against violent jihadist extremism. 
 
 Falluja residents reached by telephone late Friday said the seesaw battle had traumatized them. 
 
 “We are scared — my kids keep crying from the sounds of shelling,” Azher Qasim said. “I have a sick son, and I need to buy medication for him, and no stores are open. We have no food, or heat, and our only light is candles.” 
 
 An Iraqi special forces soldier reached by telephone on Friday said he was holed up with his men in Ramadi, sending information for airstrikes to superiors. The soldier, who spoke on the condition that his name not be used, described fierce fighting on Friday, and said his patrol had been targeted by suicide bombers. 
 
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 “We have orders to kill any gunmen in the street,” he said. “When we catch one, we kill him immediately. There is no arrest.” 
 
 The soldier said he had been facing some of the most intense fighting of his life. “When we first entered Ramadi, it was like hell opened a door,” he said. “For me, I have one idea in my mind — that I have to fight with no mercy, or I will die.” 
 
 The government has reportedly used airstrikes, with Russian helicopters that were recently purchased. 
 
 Since the withdrawal of American soldiers at the end of 2011, the United States, in an effort to influence the government, has maintained a multibillion-dollar program to sell weapons to the Iraqis. But the slow pace and the bureaucracy involved — not to mention the fact that many of the weapons, like F-16 fighter jets, have little practical use against Qaeda cells — have frustrated the Iraqis, who have increasingly looked elsewhere, especially Russia. 
 
 More recently, as the Sunni insurgency has gained strength, the United States has said it was rushing missiles and surveillance drones to Iraq. 
 
 By Friday evening, reports emerged from contested areas in Anbar of government shelling and civilian casualties. An official at a hospital in Falluja said the hospital had received the bodies of three civilians killed in the shelling and had treated 30 others who were wounded, including at least four children. Late Friday, security officials in Anbar said 86 people had been killed in the day’s fighting. ||||| The toll of the desertions came into sharp relief on Tuesday, as soldiers and their commanders abandoned bases in Mosul, all but ceding Iraq’s second-largest city to extremist fighters belonging to the Islamic State of Iraq and Syria. 
 
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 The fleeing troops left weapons, vehicles and even their uniforms behind, as militants took over at least five army installations and the city’s airport. In a desperate bid to stem the losses, the military was reduced to bombing its own bases to avoid surrendering more weapons to the enemy. American officials who had asserted that the $25 billion that the United States had spent on the Iraqi security forces would prepare them to safeguard the country after American troops left were forced to ponder images from Mosul of militants parading around captured Humvees. 
 
 The crisis has been picking up momentum as Sunni extremists have gained power and territory across the north and west of the country — and as soldiers have been leaving their posts. 
 
 In interviews over several days, soldiers and army commanders said the desertions had become widespread, with thousands of men laying down their arms, gutting front-line units across the country. Before the troops dissolved in Mosul, the army was losing as many as 300 soldiers a day, between desertions, deaths and injuries, according to a security analyst who works with the Iraqi government and requested anonymity because he was not authorized to speak publicly about the military. 
 
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 One former soldier who would give only his first name, Mohamed, because deserting is illegal, said that he had served in Ramadi and that his colleagues started deserting months ago as the deaths started mounting. “I felt like I was fighting armies, not an army,” said Mohamed, 24. 
 
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 The militants came in waves, sending suicide bombers when their ammunition grew scarce. Mohamed said that eight of his friends had died and that he almost did, too, when a mortar shell struck his Humvee. When militants singled him out as a target for assassination, forcing him to flee, it was almost a relief. 
 
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 “I’m tired,” he said. “Everyone is tired.” 
 
 The government has played down the scale of the crisis, in part by registering soldiers as “missing” rather than as deserters. Officials also blamed the problem on unrelated issues — saying, for instance, that soldiers were not returning from home leave, but only because roads leading to the battlefields had become unsafe. 
 
 Lt. Gen. Rashid Fleih, the commander of operations in Anbar Province, said last week that recent successes by the army in clearing several highways would resolve that issue. “Now the soldier who is on leave can go back to his unit without any problems,” he said. After the defeat in Mosul, though, the crisis could not be so easily brushed away. For the first time on Tuesday, the government publicly invoked the law forbidding desertions, threatening harsh punishments, including the death penalty, according to a media adviser for the prime minister, Nuri Kamal al-Maliki. 
 
 The government, though, seemed to have limited leverage. In interviews, several deserters cited the ferocity of the battle as their primary reason for leaving. They spoke of nerve-racking patrols in remote areas or in contested cities, surrounded, at times, by hostile residents. They searched booby-trapped houses and traveled roads full of bombs. Most terrifying, though, they said, were the snipers. 
 
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 Their stories added detail to the brutal shadowy war between the militants and the army — the latest trauma for a country still reeling from the American invasion and occupation and the sectarian civil war that followed. 
 
 The Growing Strength of ISIS A broader Sunni insurgency that has been growing in neighboring Syria has shown increased audacity in Iraq. The Islamic State in Iraq and Syria , or ISIS, is an expanded version of Al Qaeda in Iraq that controls a number of cities in northeastern Syria and western Iraq. Its brutal tactics alienated it from the Syrian rebel movement, as did the fact it has emphasized the establishment of an Islamic state over the fight against Mr. Assad. It was officially disowned by Al Qaeda in February. 
 
 The Sunni insurgent group has emerged as the leading force for the foreign fighters streaming into Syria, exploiting the chaos of the civil war as it tries to lay the groundwork for an Islamic state. 
 
 Al Qaeda’s central leadership cut ties with ISIS earlier this year as it rushed to build an Islamic state on its own terms, antagonizing the wider Syrian rebel movement. 
 
 Some soldiers said their families begged them to leave the service. One 25-year-old deserter said his mother was so terrified of the fighting that she burned his uniform every time he returned home on leave. Two months ago, he said she raised the stakes, threatening to kill herself if he returned to his unit. 
 
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 “We lost so many troops — I lost three or four of my friends,” said the former soldier, who was sent straight to the front line in Falluja after basic training. “The fighting was so fierce.” 
 
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 The desertions threaten to transform Iraq’s vicious conflict into something even more dangerous, by starving the government of fighters as it struggles to recapture lost territory: in Falluja, which was taken over by the militants six months ago, and now in Mosul. With fewer men to face the militants, the army is relying on artillery and airstrikes — including, human rights workers say, the use of indiscriminate barrel bombs — increasing the risks to civilians. 
 
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 As the army falters, Shiite militias are also playing a growing role in the conflict, nudged toward the fight by the government of Mr. Maliki. As the militiamen face radical Sunni jihadists, the threat of a wider sectarian conflagration grows. 
 
 The desertions of men like Mr. Halbousi — a Sunni in an army dominated by Shiites, the majority sect in Iraq — is another dangerous development. “It reinforces the sectarian polarization,” said Hayder al-Khoei, an Iraqi researcher and associate fellow with Chatham House, a policy research group in London. 
 
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 So did the government’s statements, with its “not so subtle references to a religious war"— an echo of the jihadists’ sectarian speech, Mr. Khoei said. 
 
 But above all, the soldiers — young men from southern Iraq, or the outskirts of Baghdad, who joined the service for its relatively good salary — felt “abandoned,” Mr. Khoei said. 
 
 “They are thrown into this fire,” he said. “It’s a nightmare.”
– A decade ago, the city of Fallujah became a not-so-pleasant reference point for Americans following the Iraq war as US forces dug in against insurgents. Today the American troops are gone, an al-Qaeda group has claimed the city as an Islamic state, and fighting between militants and Iraqi forces have claimed at least 60 lives in the last two weeks alone, reports AP. But you don't have to tell any of that to the US vets who fought there, if a Washington Post story is any reflection. They're following today's developments with anger and bitterness. Sample quotes: “Could someone smart convince me that the black flag of al-Qaeda flying over Fallujah isn’t analogous to the fall of Saigon?” a former Army captain wrote on Twitter. “Because. Well.” “It brings back a lot of anger,” says another vet. "I feel like it’s been a big waste of time. It’s kind of like, why the hell did all my buddies die there for? There’s no purpose to it.” But the views aren't entirely negative: “You bounce back and forth between: Was it a complete failure, or did we do the best we could and handed it over to them when things were relatively calm?” says former three-star Gen. Mark Hertling. “Every person who served in Iraq or Afghanistan never loses that part of them when they come home. It becomes part of their soul.”