Yes. But decimation, as far as I know, was something the Romans did to their own divisions for "unsatisfactory" services. But regarding Afghanistan, if you crucify a few thousand men, women and children every day for the smallest offence, resistance breaks fast.
By the way, the losses of the US in the Vietnam war were minimal too. They lost 60.000 People. In the 10 years or what, I assume they lost more people in traffic accidents and suicides. Just to put numbers a little bit into perspective.