Anthropologist Morton Fried proposed that most surviving tribes do not have their origin in pre-state tribes, but rather in pre-state bands. Such "secondary" tribes, he suggested, developed as modern products of state expansion. Bands comprise small, mobile, and fluid social formations with weak leadership. They do not generate surpluses, pay no taxes, and support no standing army. Fried argued that secondary tribes develop in one of two ways. First, states could set them up as means to extend administrative and economic influence in their hinterland, where direct political control costs too much. States would encourage (or require) people on their frontiers to form more clearly bounded and centralized polities, because such polities could begin producing surpluses and taxes, and would have a leadership responsive to the needs of neighboring states (the so-called "scheduled" tribes of the United States or of British India provide good examples of this). Second, bands could form "secondary" tribes as a means to defend against state expansion. Members of bands would form more clearly bounded and centralized polities, because such polities could begin producing surpluses that could support a standing army that could fight against states, and they would have a leadership that could co-ordinate economic production and military activities.