Pakistani military forces were unwilling to provide American and NATO commanders with the locations of all such outposts, and during the November mission, U.S. forces were reluctant to pinpoint for Pakistani coordination personnel the exact coordinates of the firefight.
The result was confusion at every level, from the commander leading the U.S. ground assault team to midlevel headquarters staff to NATO commanders.
The military's report found that U.S. forces fired in self defense and with proper force.
But it also concluded poor cooperation between American and Pakistani military officials, as well as a reliance on insufficient mapping data, was to blame.
At several times during the morning briefing, Clark and Pentagon press secretary George Little reiterated the probe's bottom-line finding: a fundamental lack of trust between America and its reluctant ally Pakistan.
The probe's findings have been shared with Pakistani officials, but only generally, the Pentagon said Thursday. A detailed briefing has yet to occur, with Little saying the Pentagon moved forward with unveiling the findings "because of leaks."
Further highlighting the nations' frosty relations, Pakistani military officials declined to participate in Clark's investigation.
Clark acknowledged during the press briefing that testimony from Pakistanis involved on the night in question is an aspect "that is missing."
The deadly November airstrike was just the latest in a string of events that have created new tensions between Washington and Pakistan.
Pentagon and Obama administration officials have been critical of their Pakistani counterparts but say rebuilding a solid working relationship is essential to the Afghanistan war effort.
The relationship was already showing signs of strain this spring. But it began to quickly erode when American commandos killed Osama bin Laden near Islamabad in early May.
Since then, U.S. lawmakers have called for the Obama administration to get tough with Pakistan. Some have said it is time to cut off the financial and military aid that has flowed from Washington to Pakistan since the onset of the U.S. war in Afghanistan.
On Thursday, Little said U.S. officials hope to begin mending the "fundamental trust" that is "lacking" in the relationship.
To that end, Little said Joint Chiefs Chairman Gen. Martin Dempsey within the last 24 hours has discussed the investigation's findings with the head of Pakistan's military. He described the conversation as "professional and cordial."