Just weeks before Blackwater guards fatally shot 17 civilians at Baghdad’s Nisour Square in 2007, the State Department began investigating the security contractor’s operations in Iraq. But the inquiry was abandoned after Blackwater’s top manager there issued a threat: “that he could kill” the government’s chief investigator and “no one could or would do anything about it as we were in Iraq,” according to department reports.

American Embassy officials in Baghdad sided with Blackwater rather than the State Department investigators as a dispute over the probe escalated in August 2007, the previously undisclosed documents show.