Newly revealed testimony from top military commanders involved in the U.S. response to the Benghazi attacks suggests that the perpetrators of a second, dawn assault on a CIA complex probably were different from those who penetrated the U.S. diplomatic mission the evening before and set it ablaze, killing Ambassador Chris Stevens and another American.

The second attack, which killed two security contractors, showed clear military training, retired Gen. Carter Ham told Congress in closed-door testimony released late Wednesday. It probably was the work of a new team of militants, seizing on reports of violence at the diplomatic mission the night before and hitting the Americans while they were most vulnerable.

The testimony, which The Associated Press was able to read ahead of its release, could clarify for the first time the Sept. 11, 2012, events that have stirred bitter recriminations in the U.S., including Republican-led congressional investigations and campaign-season denunciations of the Obama administration, which made inaccurate statements about the attacks. The testimony underscores a key detail that sometimes has been lost in the debate: that the attacks were two distinct events over two days on two different buildings, perhaps by unrelated groups.

The U.S. government still has not fully characterized the first attack in which, according to Ham and eight other military officers, men who seemed familiar with the lightly protected diplomatic compound breached it and set it on fire, killing Stevens and communications specialist Sean Smith. A disorganized mob of looters then overran the facility.

In testimony to two House panels earlier this year, the officers said that commanders didn’t have the information they needed to understand the nature of the attack, that they were unaware of the extent of the U.S. presence in Benghazi at the time and they were convinced erroneously for a time that they were facing a hostage crisis without the ability to move military assets into place that would be of any use.

The testimony reveals how little information the military had on which to base an urgent response.

Two House panels — the Armed Services and Oversight and Government Reform committees — conducted interviews with the nine officers on separate days from January to April.

Four Americans died in Benghazi, including Stevens. To this day, despite the investigations, it’s not clear if the violence resulted from a well-planned, multiphase military-type assault or from a loosely connected, escalating chain of events.

In their testimony, military officials expressed some uncertainty about the first attack, describing protests and looting in an assault that lasted about 45 minutes.

The military attache to the U.S. Embassy in Tripoli told Congress the first attack showed some advance planning. The Libyan police officer guarding the diplomatic compound fled as it began.

The defense attache, whose name wasn’t released, suggested the attackers “had something on the shelf” — an outline of a plan based on previously obtained information about the compound and its security measures, so they were ready to strike when the opportunity arose.

“They came in, and they had a sense of purpose, and I think it sometimes gets confused because you had looters and everyone else coming in,” he said. “It was less than kind of full, thought-out, methodical.”

Ham testified that the second attack, which killed security officers Tyrone Woods and Glen Doherty at the annex a mile from the diplomatic compound where the assault began the night before, showed clear military training. It was probably the work of a new team of militants, taking advantage after reports of violence at the first site and American vulnerability.

“Given the precision of the attack, it was a well-trained mortar crew, and in my estimation they probably had a well-trained observer,” said Ham, who headed the U.S. command in Africa. The second attack showed “a degree of sophistication and military training that is relatively unusual and certainly, I think, indicates that this was not a pickup team. This was not a couple of guys who just found a mortar someplace.”

Ham said the nearly eight-hour time lapse between the two attacks also seemed significant. “If the team (that launched the second attack) was already there, then why didn’t they shoot sooner?” he asked.

“I think it’s reasonable that a team came from outside of Benghazi,” he said of the second attack in testimony on April 9. Violent extremists saw an opportunity “and said, ‘Let’s get somebody there.'” He also acknowledged that the absence of American security personnel on the ground soon enough after the first attack “allowed sufficient time for the second attack to be organized and conducted.”

The attacks came as President Barack Obama was in a close re-election battle, campaigning in part on the contention that al-Qaida no longer posed a significant threat to the United States and that, blending the economy and the fight against terrorism, General Motors was alive but “Osama bin Laden is dead.” A terror attack on American assets could have damaged that argument.

The administration last month apprehended its first suspect, Ahmed Abu Khattala, and brought him to the United States to stand trial on terrorism charges.

The Justice Department maintains in court documents that Abu Khattala was involved in both attacks. Abu Khattala’s lawyer says the government has failed to show that he was connected to either one.

Ham, who happened to be in Washington the week of the attacks, briefed Defense Secretary Leon Panetta and Joint Chiefs Chairman Gen. Martin Dempsey. They informed the president.

Many of the military officials said they didn’t even know about the diplomatic mission in Benghazi, let alone the CIA’s clandestine installation nearby. Few knew of Stevens visiting the city that day. Given all of the confusion, Ham said there was one thing he clearly would have done differently: “Advise the ambassador to not go to Benghazi.”

(AP)