An Afghan police officer turned his weapon on US troops Sunday morning, killing four and bringing the total number of “green on blue” deaths to eight in three days.

The officer was at a remote checkpoint in southern Afghanistan. The US troops were part of the NATO force “training and mentoring the Afghan forces so that they can eventually operate [the checkpoint] on their own.” Operation is scheduled to pass to the Afghan forces in 2014.

Officials say the checkpoint came under attack by insurgents late Saturday night/early Sunday morning, at which time Afghan police started fighting with the American troops and four American military personnel were killed. Officials said they don’t whether the Afghan police officers planned to participate in the attack from the start or whether they “were somehow forced into attacking Americans troops by the insurgents.”

Either way, reading about these attacks must be surreal for our Vietnam combat vets who know firsthand what it’s like to fight a war with no clear lines. They fought in circumstances where North Vietnam’s army swept down from the north while the Viet Cong and Viet Minh often blended in with the population in South Vietnam, biding their time until they could get close enough to US troops to attack from the sides or the rear.

These continued green on blue attacks indicate we’re fighting that same kind of war again.