Civilian contractors working for the Pentagon in Afghanistan not only outnumber the uniformed troops, according to a report by a Congressional research group, but also form the highest ratio of contractors to military personnel recorded in any war in the history of the United States.

On a superficial level, the shift means that most of those representing the United States in the war will be wearing the scruffy cargo pants, polo shirts, baseball caps and other casual accouterments favored by overseas contractors rather than the fatigues and flight suits of the military.

More fundamentally, the contractors who are a majority of the force in what has become the most important American enterprise abroad are subject to lines of authority that are less clear-cut than they are for their military colleagues.

What is clear, the report says, is that when contractors for the Pentagon or other agencies are not properly managed  as when civilian interrogators committed abuses at Abu Ghraib in Iraq or members of the security firm Blackwater shot and killed 17 Iraqi citizens in Baghdad  the American effort can be severely undermined.