Even without notice two marines that are properly armed could have wiped out a lot of Libyans. Once the bullets started flying most in the mob would have turned and ran. so I don’t believe this. Yes two Marines can stop 400 people in a mob - especially if they are in a compound. Perhaps the end result would have been the same but at least there would have been a bunch of dead Libyans and an honorable end - like the Alamo.