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A Defense Department review of the shooting rampage at Fort Hood, Texas, has found the doctors overseeing Maj. Nidal Hasan's medical training repeatedly voiced concerns over his strident views on Islam and his inappropriate behavior, yet continued to give him positive performance evaluations that kept him moving through the ranks.

The picture emerging from the review ordered by Defense Secretary Robert Gates is one of supervisors who failed to heed their own warnings about an officer ill-suited to be an Army psychiatrist, according to information examined by investigators conducting the study.

Hasan, 39, is accused of murdering 13 people on Nov. 5 at Fort Hood, the worst killing spree on a U.S. military base.

What remains unclear is why Hasan would be advanced in spite of all the worries over his competence. That is likely to be the subject of a more detailed accounting by the department. Recent statistics show the Army rarely blocks junior officers from promotion, especially in the medical corps.

Hasan showed no signs of being violent or a threat. But parallels have been drawn between the missed signals in his case and those preceding the thwarted Christmas attempt to blow up a Detroit-bound U.S. airliner. President Barack Obama and his top national security aides have acknowledged they had intelligence about the alleged bomber, Umar Farouk Abdulmutallab, but failed to connect the dots.

The Defense Department review is not intended to delve into allegations Hasan corresponded by e-mail with Yemen-based radical cleric Anwar al-Awlaki before the attack. Those issues are part of a separate criminal investigation by law enforcement officials.

In telling episodes from the latter stages of lengthy Hasan's medical education in the Washington, D.C., area, he gave a class presentation questioning whether the U.S.-led war on terror was actually a war on Islam. And students said he suggested that Shariah, or Islamic law, trumped the Constitution and he attempted to justify suicide bombings, according to the information reviewed by The Associated Press.

Yet no one in Hasan's chain of command appears to have challenged his eligibility to hold a secret security clearance even though they could have because the statements raised doubt about his loyalty to the United States. Had they, Hasan's fitness to serve as an Army officer may have been called into question long before he reported to Fort Hood.

Instead, in July 2009, Hasan arrived in central Texas, his secret clearance intact, his reputation as a weak performer well known, and Army authorities believing that posting him at such a large facility would mask his shortcomings.

Four months later, according to witnesses, he walked into a processing center at Fort Hood where troops undergo medical screening, jumped on a table with two handguns, shouted "Allahu Akbar!" — Arabic for "God is great!" — and opened fire. Thirteen people were killed in the spree and dozens more were wounded.

Hasan has been charged with 13 counts of premeditated murder and 32 counts of attempted premeditated murder. He remains at a San Antonio military hospital, undergoing rehabilitation for paralysis stemming from gunshot wounds suffered when security guards fired back during the massacre. Authorities have not said whether they plan to seek the death penalty.

After the Fort Hood shooting, Gates appointed two former senior defense officials to examine the procedures and policies for identifying threats within the military services. The review, led by former Army Secretary Togo West and retired Navy Adm. Vernon Clark, began Nov. 20 and is scheduled to be delivered to Gates by Jan. 15.

Army Lt. Col. Jonathan Withington, a Pentagon spokesman, declined to comment on the West-Clark review because it's not complete. "We will not know the specific content of the report until it is submitted to the secretary of defense," he said.

Hasan's superiors had a full picture of him, developed over his 12-year career as a military officer, medical student and psychiatrist, according to the information reviewed by AP.

While in medical school at the Uniformed Services University of Health Sciences from 1997 to 2003, Hasan received a string of below average and failing grades, was put on academic probation and showed little motivation to learn.

He took six years to graduate from the university in Bethesda, Maryland, instead of the customary four, according to the school. The delays were due in part to the deaths of his father in 1998 and his mother in 2001. Yet the information about his academic probation and bad grades wasn't included in his military personnel file, leaving the impression he was ready for more intense instruction.

In June 2003, Hasan started a four-year psychiatry internship and residency at Walter Reed Army Medical Center in Washington, D.C., and he was counseled frequently for deficiencies in his performance. Teachers and colleagues described him as a below average student.

Between 2003 and 2007, Hasan's supervisors expressed their concerns with him in memos, meeting notes and counseling sessions. He needed steady monitoring, especially in the emergency room, had difficulty communicating and working with colleagues, his attendance was spotty and he saw few patients.

In one incident already made public, a patient of Hasan's with suicidal and homicidal tendencies walked out of the hospital without permission.

Still, Hasan's officer evaluation reports were consistently more positive, usually describing his performance as satisfactory and at least twice as outstanding. Known as "OERs," the reports are used to determine promotions and assignments. The Army promoted Hasan to captain in 2003 and to major in 2009.

At Walter Reed, Hasan's conflict with his Islamic faith and his military service became more apparent to superiors and colleagues, according to the information. He made a pilgrimage to Mecca in Saudi Arabia, a trip expected of all Muslims at least once. But he was also cited for inappropriately engaging patients in discussions about religious issues.

Early in 2007, Maj. Scott Moran became director of psychiatry residency and took a much firmer line with Hasan. Moran reprimanded him for not being reachable when he was supposed to be on-call, developed a plan to improve his performance, and informed him his research project about the internal conflicts of Muslim soldiers was inappropriate.

Nonetheless, Hasan presented the project, entitled "Koranic World View as It Relates to Muslims in the U.S. Military," and it was approved as meeting a residency program requirement, according to the information.

Hasan graduated from the Walter Reed residency program and began a two-year fellowship in preventive and disaster psychiatry. Despite his earlier reservations, Moran wrote a solid reference letter for Hasan that said he was a competent doctor.

Reached by telephone, Moran declined to comment.

Hasan completed the fellowship June 30, 2009. Two weeks later he was at Fort Hood.