The term insurgency group applies to a group of people who organize themselves to challenge the legitimacy of the recognized government and/or advance their political agenda by military means. A traditional insurgency focuses on amassing military power sufficient to overthrow the government.
Insurgency groups often struggle to adapt and overcome barriers that inhibit their ability to learn on the battlefield. For example, parochial groups can be hard to change; pumping guns and money into them might buy limited cooperation but is unlikely to lead to deep organizational change (such as the unified organization of some anti-colonial rebels in Africa or the unification of factional leaders within al-Shabaab).
Another obstacle is that many armed groups that form in the context of peripheral state challenges are rooted in social movements that have multiple factions and conflicting interests. Consequently, they are typically plagued with continuing fragmentation. This contrasts with armed groups with’movement’ origins that often have pre-existing organisational resources.
Finally, there is the problem of changing priorities once an insurgency group achieves victory. For example, the Zapatistas were content with dominating their local region instead of overthrowing a national government; this was a different strategy than that of the FARC, who wanted nothing less than total government control.
Another difficulty is that insurgents need to have a broad spectrum of financial, material and intellectual resources in order to be effective. This contrasts with pure terrorist groups that normally field fighting forces orders of magnitude larger than those of an insurgency, and whose violence replaces rather than complements a specific political programme.