While warlords are commonly viewed as regional leaders who threaten the sovereignty of a state, there are a number of states where the central government functions in collusion with warlords to achieve its goal of exercising its sovereignty over regions that would otherwise fall outside its control. In such decentralized states, particularly those where armed groups challenge national sovereignty, warlords can serve as useful allies of a central government that is unable to establish a monopoly over the use of force within its national territory.