Continuity mistake: When the G.R.S. team is on their day off (9/11 anniversary), Tanto is seen video chatting with his wife. In the frontal shot of him, he's using a Samsung smartphone, but in the next shot, it changes to a Blackberry. This is done multiple times throughout the scene.
Continuity mistake: During the first firefight with GRS at the CIA annex, Oz is firing and it pans in front of him, where we see his Night Vision Goggles have been hit and broken in half. The next shot is when he gets shot and shows his goggles getting destroyed.
Continuity mistake: More than halfway through the movie, the "Americans" set base at a really nice house. They get attacked several times while at that house. Every time the "Americans" get attacked and people died, there aren't bodies lying around the next time they get attacked, and no-one removes the bodies either.
Continuity mistake: At 8:40 PM on September 11th, the sun has not set. The sun would have set over an hour before on that date. In fact, the sun would never be shining that late; sunset on the longest day of the year is around 8:20 PM. (00:39:38)
Continuity mistake: When terrorists start to attack the Ambassador's residence, Chris Stevens is seen putting on a black plate carrier vest. The one he is seen putting on has a cummerbund which lifts up to open. However, in the next several shots and until he isn't seen again, he has a side opening vest, which is actually an IBA (Interceptor Body Armor). This armor opens like a flak jacket by pulling the left flap.
Continuity mistake: In the beginning scene when Jack Silva is being picked up at the airport he's shown getting into the range rover in a blue button down shirt, sport coat and blue jeans. When they return to the CIA annex he exits the vehicle in khaki cargo pants and a lighter button down shirt. His bags were placed in the rear cargo area of the vehicle, tier 1 operators would not stop in a hostile environment to change clothes. (00:04:10 - 00:09:35)
Answer: Ansar-Al-Sharia isn't ISIS; it was disbanded in 2017. The group the soldiers were fighting weren't ISIS, they were February 17th Martyr's Brigade. The soldiers at the end were Tripoli GRS reinforcements.