What controlled chemical substance currently hurts the military the most?

Alcohol?

Honestly, it's prescription drugs. As a supervisor, it's not easy to detect the abuse. Once you have a suspicion, it's complicated to handle.

All chemicals hurt the force. I think that the rampant abuse of drugs and alcohol is a symptom of a much larger problem that faces our veterans. The repeated deployments take their toll on people and sets the conditions for some to resort to such things. The military and other agencies need to find ways to help Soldiers cope. I know on paper they say there is no stigma and all of these classes on resilience are taking place. Honestly it is little more than a check the block thing. There must be an honest effort to address these issues in a manner that does not threaten the Soldier's career in reality or perception. When I came back from deployments there was the reintegration thing, but I like many of my comrades simply told the mental health folks exactly what they wanted to hear that everything was fine just so we could leave.