"The Pentagon blocked an attempt by Reuters to obtain the gunsight footage of the incident through the Freedom of Information Act.[25] In a personal statement during his court martial, Bradley Manning stated that the military did have access to this information, and was actively examining it, yet denied access partially on the basis that the information may no longer exist.[58]
An internal legal review by staff at Forward Operating Base Loyalty in Iraq during July 2007 stated that the helicopters had attacked a number of armed insurgents within the rules of engagement, and that in an apparent case of collateral damage two reporters working for Reuters had also been killed. The review would not be released in full until 2010, after the video of the incident had been released by WikiLeaks.[2]"
As you see the investigation started in 2007.
"Manning told Lamo that he gave WikiLeaks the video of the July 12, 2007 Baghdad airstrike after finding it in a Judge Advocate's directory.[39] WikiLeaks named it "Collateral Murder," and Assange released it during a press conference at the National Press Club in Washington, D.C., on April 5, 2010.[40] The video showed an American helicopter firing on a group of men in Baghdad. One of the men was a journalist, and two other men were Reuters employees carrying cameras that the pilots mistook for an anti-tank grenade launcher (RPG-7). The helicopter also fired on a van that stopped to help the injured members of the first group; two children in the van were wounded and their father killed. The Washington Post wrote that it was this video, viewed by millions, that put WikiLeaks on the map. According to Nicks, Manning e-mailed a superior officer after the video aired and tried to persuade her that it was the same version as the one stored on SIPRnet. Nicks writes that it seemed as though Manning wanted to be caught.[40]"
My 2 cents: As a tactical stand point. The video lets enemies know the capability of the Chopper optics and targeting systems. It gives them line of sight and peripheral vision dimension that they could use to develop tactics on how close to get to one, of which angle to use as an avenue of approach to attack. It also gave out Call Signs and Ground Unit ID's. All of which are to be guarded, remember Heraldo was kicked off the air just for drawing in the dirt.
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