WASHINGTON -- An investigation into the State Department's preparations for and management of the terrorist attack in Benghazi, Libya, has concluded that "systemic failures and leadership and management deficiencies" within the department played a major role in the devastation that took place there last September.

Four Americans were killed in the overnight raid on the compound, including U.S. Ambassador Christopher Stevens. The ensuing controversy over the incident, and the administration's handling of it, threatened to derail President Barack Obama's reelection campaign through the fall.

The new report, by an independent Accountability Review Board established by the State Department, concluded that two bureaus at the department -- Near East Affairs and Diplomacy Security -- failed to properly recognize the rising dangers of Eastern Libya despite the lack of any specific threats, and neglected the growing concerns of security analysts on the ground about the capabilities of the local Libyan guard force.

The result, the report said, was a "security posture that was inadequate for Benghazi and grossly inadequate to deal with the attack that took place."

But while the unclassified version of the report, which was released Tuesday night, is undeniably harsh in its analysis of the State Department's management ahead of the attack, it also appears to undermine a number of the more outlandish charges made during the heat of the uproar this fall.

For instance, while many figures -- led, in large part, by the news analysts at Fox News -- suggested that the administration had opted to watch the crisis unfold rather than send military reinforcements, the report found "no evidence of undue delays in decision making or denial of support from Washington."

Many critics of the administration had raised question about why a team of specially trained military operators had been dispatched to an airfield in Italy but not, apparently, sent to help fend off the attack.

Instead, the report concluded that the response by all agencies involved was "timely and appropriate," and despite speculation to the contrary, "there simply was not enough time given the speed of the attacks for armed U.S. military assets to have made a difference."

Another accusation rebutted by the report was the notion that senior-level officials had in some way refused to permit CIA operatives working out of a nearby annex to travel to the main compound to assist in repelling the attack.

That detail, first reported by Fox News, was not correct, the report said.

Instead, a "team leader" at the annex had "decided on his own" to delay leaving the facility briefly to see if local security elements would arrive with reinforcements. After "a brief delay," and determining that they would not, the team leader made the decision to move some units toward the compound, the report said.

It is also not clear from the report if the attackers of the compound were aware that Ambassador Stevens was there on the night of the attack, or if he was their target.

The night before the attack, the report notes, local media turned up at an event that the embassy had believed to be an undisclosed meeting with the Benghazi City Council, meaning that at least some people in town were aware of Stevens' visit.

But amid the frenzy of the attack on Sept. 11, the report found that Stevens did not appear to have been captured by the militants at any point, despite early photographs that appeared to show his body being dragged through the streets.

Instead, the report said that "to the best knowledge of the Board" he was delivered, unresponsive, to a local hospital by six "good Samaritans" who were among the hordes of attackers. Local doctors spent approximately 45 minutes attempting to resucitate Stevens before concluding he was dead.

The report also upholds much of the basic outline of the course of events on the ground in Benghazi as described by the State Department in a briefing for reporters that took place almost a month after the attack, and adds some striking details of bravery.

Two of the security guards accompanying Ambassador Stevens were badly wounded during the attack, the report says, noting that one suffered "a severe laceration" to his forearm while repeatedly entering a smoke-filled room in search of the ambassador, and the other was found vomiting and losing consciousness from smoke inhalation.

There were other smaller moments of bravery recognized by the report, including a nurse at the embassy in Tripoli who provided essential medical assistance to the evacuees from Benghazi, and a consular officer who donated blood that night to help save the life a of a colleague.

On the whole, however, these people on the ground were failed by their bosses in Washington, the report said, and a clunky bureaucracy that failed to recognize and adapt to a changing security situation in Eastern Libya, allowing the ambassador to travel to a place where the local security measures had repeatedly proven insufficient.

The report also acknowledged that with a vastly increased need for security at embassies and consulates in war zones, the Bureau of Diplomatic Security has been "stretched to the limit as never before."

A consistently limited budget imposed by Congress, the report added, "had the effect of conditioning a few State Department managers to favor restricting the use of resources as a general orientation," which helps explain why the local security officials' calls for more staff was not immediately heeded.

And while the report does not focus on the more heated controversy about how the Obama administration opted to share information with the public about the raid, it does make clear that the initial claim that the attack was simply an outgrowth of a larger protest is not correct. There was no protest outside the compound, the report states.

In a letter accompanying the release of the report, Secretary of State Hillary Clinton said her department was accepting all 24 of the report's recommendations.

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  • A burnt out vehicle sits smoldering in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A broken window after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • The U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A burnt car is seen after an attack on the U.S. Consulate by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Soot and debris spills out of the U.S. Consulate after an attack by protesters in Benghazi, Libya, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man looks at documents at the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. The graffiti reads, "no God but God," " God is great," and "Muhammad is the Prophet." (AP Photo/Ibrahim Alaguri)

  • A man walks on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Glass, debris and overturned furniture are strewn inside a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A man walks through a room in the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • Libyans walk on the grounds of the gutted U.S. consulate in Benghazi, Libya, after an attack that killed four Americans, including Ambassador Chris Stevens, Wednesday, Sept. 12, 2012. (AP Photo/Ibrahim Alaguri)

  • A vehicle and the surrounding area are engulfed in flames after it was set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • An armed man waves his rifle as buildings and cars are engulfed in flames after being set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle burns after it was set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle sits smoldering in flames after being set on fire inside the US consulate compound in Benghazi late on September 11, 2012. (STR/AFP/GettyImages)

  • A vehicle and surrounding buildings smolder after they were set on fire inside the US consulate compound in Benghazi, late on September 11, 2012. (STR/AFP/GettyImages)

  • LIBYA CONSULATE

    Map locates Benghazi, Libya, where the U.S. ambassador to Libya and three other Americans were killed in an attack