It's four years after Zero Hour, with remenants of the GLA still in existance and the US trying it's best to eliminate the GLA threat all together with the aid of China. A new group comes into play, the Militia. While not militarily funded, they are a heavily armed group of fighters armed to the teeth with homemade weapons and vehicles. The Militia being civilian in nature are at home fighting in urban areas, and gain bonuses while doing so. While the Militia will aid in the elimination of the GLA, they still do not like China or the US due in large part to the war being brought to the Militia's door step.
You can see the missile pods in this one and get a
better idea of what they look like.