The U.S. soldier charged in the Fort Hood military base shooting that killed 13 went on trial Tuesday, and he was likely to face victims for the first time since he shouted "Allahu Akbar!" _ Arabic for "God is great!" _ and opened fire.

Nidal Malik Hasan, an Army psychiatrist, has never denied carrying out the 2009 attack on his fellow soldiers _ one of the worst mass shootings in U.S. history. He is representing himself at a trial charging him with murder and attempted murder for the attack that also wounded more than 30. That means he could end up questioning his victims directly.

Military prosecutor Col. Steve Henricks told jurors Hasan planned to "kill as many soldiers as he could," and he said the prosecution will show jurors that Hasan picked the date of the attack _ Nov. 5, 2009 _ for a reason.

Hasan told jurors that "the evidence will clearly show that I am the shooter." He said it also would show "that we are imperfect Muslims trying to establish the perfect religion. ... I apologize for any mistakes I made in this endeavor."

The evidence presented during the trial will only show one side, he added.

Hasan, a U.S.-born Muslim of Palestinian descent, has wanted to argue that he carried out the shooting in "defense of others" _ Muslim insurgents fighting U.S. soldiers in Afghanistan _ but the judge denied that strategy. The judge also said he will not be able to make speeches about his beliefs.

On the witness stand will be many of the wounded, plus dozens of others who were inside the post's Soldier Readiness Processing Center, where service members went to prepare for deployment.

Henricks told jurors that Hasan tried to clear the area of civilians as he walked through and opened fire inside the building, where service members were preparing to deploy to Afghanistan. Hasan only shot at one civilian who tried to stop him, Henricks said.

The trial opened under heavy security. Guards with assault rifles stood watch outside the courthouse, which was almost entirely hidden by stacks of heavy, shock-absorbing barriers that extend to the roofline.

Hasan, who was shot in the back by officers responding to the attack, is now paralyzed from the waist down and uses a wheelchair.

Alonzo Lunsford, who was wounded, is expected to testify.

"That man strikes no fear in my heart. He strikes no fear in my family," Lunsford said. "What he did to me was bad. But the biggest mistake that he made was I survived. So he will see me again."

But Shawn Manning said he dreaded the expected confrontation.

"I have to keep my composure and not go after the guy," said Manning, a mental health specialist who was preparing to deploy to Afghanistan with Hasan. "I'm not afraid of him, obviously. He's a paralyzed guy in a wheelchair, but it's sickening that he's still living and breathing."

Hasan's defense strategy remains unclear. He has released statements to media outlets about his views on the Islamic legal code known as sharia and how it conflicts with American democracy. The government has said that Hasan sent more than a dozen emails starting in December 2008 to Anwar al-Awlaki, a radical U.S.-born Islamic cleric killed by a drone strike in Yemen in 2011.

If Hasan is convicted and sentenced to death, it likely would be decades before he goes to the death chamber, if at all. The military has not executed an active-duty soldier since 1961. Five men are on the military death row, but none is close to an execution date.

Eleven of the 16 death sentences handed down by military juries in the last 30 years have been overturned, according to an academic study and court records.

That's one reason why prosecutors and the military judge have been careful leading up to trial, said Geoffrey Corn, a professor at the South Texas College of Law and former military lawyer.

"The public looks and says, `This is an obviously guilty defendant. What's so hard about this?'" Corn said. "What seems so simple is in fact relatively complicated."

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AP National Writer Allen G. Breed and Associated Press writers Nomaan Merchant and Ramit Plushnick-Masti contributed to this report.