Michael Murphy SDVT-1
Danny Dietz SDVT-2
Matt "Axe" Axelson SDVT-1
Marcus Luttrell SDVT-1
They were all seconded to Seal Team 10 in Afghanistan
Afghani goat herders comprimised their secret mission to track a Taliban leader. Killing them would be a violation of the ROE (Rules of Engagement). Holding them would reveal their position. Letting them go would likely bring the Taliban upon them.