Story highlights December 31 is the anniversary of "Iraq Day," also known as "Day of Sovereignty"

The day marks the official end of the U.S.-led war in Iraq

Iraqis and Americans remain uncertain about the country's future

U.S. Army captain: "We're all kind of watching ... trying to figure out if it was worth it"

When the first U.S. military convoy rolled into 8-year-old Saad Kareem's middle class neighborhood in Baghdad nearly a decade ago, he was scared, even as others around him whistled and danced.

Saad's family is Shiite, and the U.S. invasion brought hope for political and religious freedoms they'd missed under Saddam Hussein's Sunni-dominated regime.

"I was with my mother at the time, holding my mother's hand very tight. I was so scared because I thought that they were coming to kill us," recalled Saad, now 17. "But when I saw my mother smiling, I relaxed."

The safety Saad felt in that moment proved elusive: First there was war, then sectarian strife that pitted Sunni extremists against Shiite militants and brought Iraq to the brink of civil war.

Then came the official end of the war. On December 31, 2011, the country celebrated " Iraq Day " and the departure of U.S. troops. As Iraq prepares to mark the anniversary, also known as the "Day of Sovereignty," last year's celebratory tone has been replaced by a more somber one.

Prime Minister Nuri al-Maliki's political bloc, the Islamic Dawa Party, called on Iraqis not to become divided along sectarian or ethnic lines by "malicious schemes." The country has struggled to define itself, as its government stumbles from one political crisis to another.

Just as the last U.S. troops withdrew, al-Maliki, a Shiite, moved to arrest Vice President Tariq al-Hashimi, a Sunni, who al-Maliki accused of using his security detail as a hit squad.

More recently, a few days before the first Iraq Day anniversary, thousands of Sunnis took to the streets in Anbar province, a major trade thoroughfare to Jordan and Syria, to protest al-Maliki's order to arrest the bodyguards of Finance Minister Rafaie Esawi, a Sunni. The arrest of Esawi's bodyguards came just hours after President Jalal Talabani, a Kurd who is widely viewed as a stabilizing political force in Iraq, left the country to undergo treatment for cancer in Germany.

Photos: Last U.S. troops leave Iraq Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Boot footprints are seen in front of U.S. Mine Resistant Ambush Protected (MRAP) vehicles in the nearly deserted Camp Adder, now known as Imam Ali Base, on December 16. Hide Caption 1 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Soldiers from the 3rd Brigade, 1st Cavalry Division bow their heads in prayer during a casing of the colors ceremony while preparing to depart from Iraq at Camp Adder, now known as Imam Ali Base, near Nasiriyah, Iraq. Hide Caption 2 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Soldiers rejoice in the convoy staging area before departing Camp Adder. Hide Caption 3 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Soldiers (left to right) Peter Nemmers, Morgan Bright and Matthew Hildebrandt from the 3rd Brigade, 1st Cavalry Division laugh while preparing to depart from Iraq at Camp Adder. Hide Caption 4 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Specialist Shunterika Lewis from the 3rd Brigade, 1st Cavalry Division laughs while preparing to depart in the last convoy from Iraq at Camp Adder. Hide Caption 5 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Soldiers from the 3rd Brigade, 1st Cavalry Division toss out trash while preparing to depart in the last convoy from Iraq. Hide Caption 6 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – U.S. Mine Resistant Ambush Protected (MRAP) vehicles drive through Camp Adder before departing what is now known as Imam Ali Base on December 16. Hide Caption 7 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – Soldiers from the 3rd Brigade, 1st Cavalry Division board a C-17 transport plane to depart from Iraq at Camp Adder, now known as Imam Ali Base, on December 17 near Nasiriyah, Iraq. Hide Caption 8 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – One of the first U.S. Humvees cross the Iraq-Kuwait border on December 18 to signify the "tactical road march" out of the combat zone. Hide Caption 9 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – A U.S. soldier gives a thumbs up from the roof of his brigade's Humvee while crossing the Iraq-Kuwait border. Hide Caption 10 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – U.S. and Iraqi troops line up as the final U.S. Army convoy crosses the border from Iraq into Kuwait. Hide Caption 11 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – A U.S. cargo trailer crosses the Iraq-Kuwait border for the final time. Hide Caption 12 of 13 Photos: Last U.S. troops leave Iraq Last U.S. troops leave Iraq – U.S. and Iraqi commanders shake hands to mark the end of the United States' presence in the Iraq combat zone. Hide Caption 13 of 13

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Iraq's Arab Sunnis and Kurds have accused al-Maliki and his Shiite political party of working to consolidate power in Iraq by cutting them out of the political process, an allegation that comes as U.S. lawmakers raise concerns about Iraq strengthening its ties with Shiite-dominated Iran.

One year after U.S. troops left, much about a post-war Iraq remains unclear -- for the Iraqis recovering from war, and still facing bombs and battles; for Americans re-adjusting to life in the United States and wondering whether their work was worthwhile.

This time last year, there was cautious optimism among Saad's family members. It seemed possible the political instability and violence that plagued Iraq might ebb. In its place, Saad's family hoped a safer, more stable Iraq would emerge.

Today, at Saad's all-male high school in central Baghdad, talk routinely centers on the latest bombing or bubbling sectarian tensions -- Sunni versus Shiite, Arab versus Kurd. There are concerns, Saad said, about the possible return of al Qaeda in Iraq, a group of primarily Sunni extremists bent on reigniting sectarianism. The latest political crisis is split along sectarian lines and has raised fears that political strife could translate into violence on the streets.

Even with a dramatic decline in violence in Iraq from the height of the war, bombings and gun battles remain a near-daily occurrence. A car bomb killed Saad's best friend, and he's no longer allowed to walk to school. His father drives him instead.

Saad has vowed after graduating high school, he will leave Iraq. For good.

"Sometimes," Saad said, "I ask myself why God did not create me in another country."

'I don't think ... I really understood it'

U.S. Army Spec. Brittany Hampton looked out the window of the armored vehicle as it rolled down the highway.

Somehow, it was fitting that the 22-year-old woman who had seen her father off for the start of the Iraq war almost nine years earlier would be among the very last soldiers in the very last vehicle in the very last convoy to leave the country.

"I don't think that day I really understood it," she said nearly a year later.

Hampton, a medic, knew crossing from Iraq into Kuwait meant the end of the war for her and her fellow soldiers. But the historic nature of the moment hit her months later, when she was standing in front of the vehicle nicknamed "Praetorian 7" for the elite Roman guard unit that once protected Roman emperors.

It was there, outside a museum at Fort Hood, Texas, it became clear.

"That's sort of when I knew it was a big deal, seeing the truck out there with all these other historic vehicles," she said.

Hampton, who lives in Killeen, Texas, was an "Army brat," the child of a soldier. In the fifth grade, she was assigned to outline what she wanted to be when she grew up, so she wore her father's uniform to school.

It seemed like a natural step to join the Army, and it was no surprise when she got orders to deploy to Iraq.

Her father never really talked about his time there. After his second deployment, he wasn't the same, she said. He refused to go through the drive-in, and he didn't like crowded stores.

It was likely difficult for him to see how she'd changed, she said.

"When he left, I was a little girl," she said. "I had a cell phone and a boyfriend when he came back."

By the time Hampton got to Iraq, the end of the war was in sight. There was still the daily threat of roadside bombs and rocket attacks to contend with, but nothing like her father had seen at the height of the war.

In the year since she rolled across the Iraq-Kuwait border, Hampton got engaged to a fellow soldier.

As she looks toward starting a family, Hampton's made another decision: She's getting out of the Army.

"I honestly don't think I want to put my children through that," she said.

"It's really hard."

'I don't want to live like this'

Ali Adel waited his turn for a haircut in a small barbershop nestled between short, squat buildings near his neighborhood mosque.

One minute, he was making small talk with patrons. The next thing the 20-year-old remembers is lying in a Baghdad hospital bed, writhing in pain.

He had no memory of the November 27 blast, a bombing that took place nearly a year after the last U.S. troops left Iraq.

"I never thought this would happen to me," Adel said, lying in a bed at his family home.

Over the years, Adel had seen the devastation caused by bombings that repeatedly struck his neighborhood in the predominantly Shiite district of Shula. For years following the U.S.-led invasion of Iraq, Sunni extremists targeted the al-Zahraa mosque in his neighborhood with deadly results.

When U.S. troops withdrew from Iraq, Adel was hopeful that maybe the violence, the bombings, might stop.

Adel was 11 during the 2003 invasion. Today, he measures life in Iraq by "before" and "after."

Before the war, when Saddam Hussein was in charge, and after the war, when he was deposed. Before the war, when his family was whole, and after the war, when he lost friends and family members to insurgent attacks.

A month after the bombing, his head remains bandaged from a shrapnel wound. He can't see out of his right eye.

He's counting the days until he can go back to work as a construction day laborer.

"I don't want to live like this, I want to go back to a normal life," he said.

'Trying to figure out if it was worth it'

U.S. Army Capt. Mark Askew had seen some of the very worst of the fighting in Iraq, battling insurgents street by street in 2007 as part of a strategy that saw thousands of American troops push into areas held by Sunni militants and hold it.

Askew also saw positive changes take hold in Iraq, from its military taking responsibility for security to its lawmakers standing up a fledgling democracy.

When he left last year, on the last U.S. military convoy to leave the country, he wondered what would happen to Iraq.

Askew, who is 29, was at West Point when the war began in 2003. He watched its beginnings like many Americans -- on television.

He first stepped foot in Iraq in 2007 as part of then-President George W. Bush's "surge" policy: Push into territory held by Sunni militants and hold it.

His assignment was Mosul, 400 kilometers north of Baghdad, where Iraqi security forces were struggling to hold the city. It was there that Askew first learned the human cost of war: His executive officer was killed in a roadside bomb, leaving him briefly in charge while awaiting a replacement.

"I grew up on my first deployment," said Askew, who lives in Tampa, Florida. "It made me appreciate my family more. It made me appreciate politically what we have."

Askew returned to Iraq in 2011 with a military police unit. He was charged with securing U.S. troops at bases in the southern Shiite heartland where they were routinely targeted by Iranian-backed insurgents.

Even as he left Iraq, he wondered about the country's future: Will Iraq be stable? Will its government align itself with Iran?

The same questions have been asked by a number of Americans, from lawmakers to soldiers, as reports emerge that the United States has warned Iraq against allowing Iran to use its airspace to ship weapons to Syria, its ally.

"We're all kind of watching Iraq right now, and trying to figure out if it was worth it," he said.

'I see no good future for Iraq'

Last year, on "Iraq Day," Mahdi Auda Ghanam's family celebrated.

This year, the 25-year-old's family is in mourning. Ghanam was killed by a car bomb as he walked to a small repair shop he operated in the Shula district. It was the same November attack that wounded Adel.

"We were happy, and I distributed candies to neighbors when the Americans left Iraq last year. We thought the war was over and there would be no more killing and destruction," Ghanam's mother, Mahdiya, said. "I don't know who to blame. They said al Qaeda, but where is al Qaeda? I blame those who don't fear God."

In the months and days before Ghanam's death, he worried the deteriorating security situation, his family said.

Still, he was making plans for the future. He had fallen in love and was going to get married, his mother said. He still played in the neighborhood soccer league, and he was looking for a permanent job with the government.

But with the rise in car bombings, he took precautions.

"So many times, Mahdi canceled a planned trip to go to the ... market to buy stuff for his store never knowing that instead one day he would die inside his store," Ghanam's brother, Ali, said.

The family won't participate in the upcoming elections because they don't believe it will make a difference, he said.

"If you ask me if I am optimistic about the future of Iraq, I really don't have an answer. Maybe a year ago, I would have said I am maybe optimistic. But now I'm just not sure," Ali Ghanam said.

"I see no good future for Iraq if this continues."