GLA troops fight under a just cause to free the world from tyranny and exploitation by the world powers, which particularly made them very dedicated to the cause. Therefore, GLA fighters can be whipped into a more potent killing frenzy through the Fanatical Devotion upgrade, issued from the Chemical Lab.
The upgrade gives Angry Mobs AK-47 assault rifles and Molotov cocktails that increases their firepower, allowing them to quickly dispatch most ground units in their way. It also significantly boosts the speed of Hijackers and Terrorists, allowing them to close to unsuspecting targets before they could react.
Behind the scenes
Prior to 1.87 this upgrade is named Arm the Mob and only affects Angry Mobs, which also increases their range by 25%. It also costs only $1000 and are available from the Black Market.