It's possible that Barr favored post-9/11 retalitory strikes and a mission to go get bin Laden but opposed the occupation of Afghanistan. That is, roughly, the Ron Paul position. But given that overthrowing the Taliban government was a prerequisite for such a mission, I'm not sure how an occupation for at least some time period could have been avoided. And I agree it makes no sense to say the Afghan war is not a military intervention.