Advanced Assault Infantry from Killzone 2
The Advanced Assault Infantry are elite special forces soldiers of the Helghan Army. They are identical to the regular Assault Infantry, but more heavily armored and skilled at combat. While they do prefer utilising cover as the regular Assault does, they won't hesitate to charge in for melee attacks if you get too close.
Analysis
You can deal with Advanced Assault Infantry in the same manner as you would handle the regular Assault Infantry. There are a few notable exceptions though. The Advanced Assault has more health meaning it will take more gunfire to put them down, so be mindful of this if you rush them for an R&G attack.
This enemy has also a better aim and tends to fire faster than regular Assault, so again be mindful of getting too close or staying out in the open too long when more than one is around. As with the regular Assault, they constantly seek cover. When they achieve crouching cover, always zoom-in and target the tops of their heads that you can just barely see over the cover point. When they seek standing cover, their elbow or leg will usually be exposed, so don't hesitate to fire on any body part that you can target. If more than one is at the same cover point, the use your grenades to take them all out quickly.
Notably, their helmets will not deflect a headshot, unlike the helmets worn by the lower-ranking Assault Infantry soldiers.
Killzone 3
Advanced Assault Infantry appear in the last two missions of Killzone 3, The Reckoning and Interception. They are the primary enemies fought throughout The Reckoning, and a number of them appearing supporting the platoon of LMG Troopers defending the Helghast space station in Interception.
Intel
Health: 75
Weapons: StA52 Assault Rifle, M194 Percussion Grenade
First Appearance: Suljeva Village: Maintenance Office
Trivia
The Advanced Assault Trooper does not appear on killzone.com, however he is both displayed in the "Killzone 2 Fansite Kit", better known as 'Unlockable 4', and in the Killzone 2: Collector's Guide to Campaign and Warzone.