Alaa al-Qureishi's home is full of ghosts — the photos of dead relatives decorating the walls of every room.

In 2006, his mother and brother were killed when the house, in the Sadr City neighborhood of Baghdad, was randomly hit by a rocket. A year later, tragedy struck again when two more brothers and his brother-in-law were killed in sectarian violence at the height of the country's civil war.

Today, many of his fellow Shiites are on the front lines battling the extremists of the Islamic State group in what many see as an existential threat to Iraq. But the 37-year-old al-Qureishi is sitting this one out.

"Our situation keeps going from bad to worse," he said, his eyes filled with tears, the pain of his loss still fresh. "My family doesn't need any more martyrs."

Twelve years after the U.S. invaded Iraq to topple Saddam Hussein and eliminate weapons of mass destruction that were never found, the country is still mired in war.

The Islamic State group, also known as ISIS or ISIL, rules more than a third of Iraq. Powerful, often violent, Shiite militias — armed and advised by Iran — are leading the fight against the extremists, propping up Iraq's humiliated military, which crumbled in the face of the militant threat last year.

U.S. forces are back, albeit in a non-combat role, thrusting open a door that many had sought to close for good when American troops withdrew in late 2011.

For Iraqis, the various conflicts feel like one long war, which many blame on the United States. A common view is that overthrowing Saddam spurred the explosion of sectarianism that followed when the long-oppressed Shiite majority rose to power.

A country beleaguered by foreign invasion and civil war became vulnerable to extremism. Fueled by another civil war in neighboring Syria, that extremism grew into al-Qaida in Iraq and later, morphed into the Islamic State group that is now spreading havoc in several countries across the Arab world.

"Obviously, there is a threat that you can trace that shows Daesh emerged because of the invasion," said Sajad Jiyad of the Iraqi Institute for Economic Reform, using another acronym for the Islamic State group. "It's the lack of rule of law, randomness of the violence and brutality that we see on a daily basis today that shocks people."

The U.S.-led invasion that began in March 2003 was initially touted as the dawn of a new, democratic era for Iraq.

There was the "shock-and-awe" campaign; a dictator found hiding in a spider hole; national unity governments; insurgents, militias and retribution; and sectarianism and civil war.

More than 500,000 Iraqis were reportedly killed in the eight-year war, while more than 3,500 U.S. soldiers died in combat.

Hundreds of thousands of Iraqis fled the country during that war. Today, more than 2 million are displaced from the violence set off by the campaign by the Sunni militants of the Islamic State group to establish a self-declared caliphate.

Iraq has staggered economically, despite its oil wealth. The International Monetary Fund forecasts that the economy shrank by 2.75 percent in 2014 — its first contraction since 2003.

Na'ma Ali Saleh, a 52-year-old resident of Sadr City, has struggled to keep a steady job since the invasion and believes the country's current crisis makes finding work impossible.

"We have hot weather, and half of the time, there is no power or water," he said. "Saddam was a disaster for Iraq, but at least in those days, we only feared one man. Now, we fear many."

Nostalgia for life under Saddam is rampant, despite his heinous criminal record that included the hangings of Shiite politicians, unlawful detentions and the disappearance of hundreds of political dissidents, and a massacre of between 50,000 to 100,000 Kurdish Iraqis.

"Iraqis are still waiting for a better alternative," Jiyad said. "At least in Saddam's time, there was some semblance of rule of law," he added. "He was violent, but it was targeted."

Three of al-Qureishi's late brothers were imprisoned under Saddam, accused of political dissent. But he now believes that was a small price to pay for the relative stability the country once enjoyed.

"What's worse? Prison or death?" he asked, visibly distraught. "I may be doing my country a service by fighting in the war against Daesh, but I will do my family a much bigger disservice if I go to fight and die."