In 1973, the Polisario Front was formed in a revival of militant Sahrawi nationalism. The Front's guerrilla army grew rapidly, and Spain lost effective control over most of the territory by early 1975. Its effort to found a political rival, the "Partido de Unión Nacional Saharaui" (PUNS), met with little success. Spain proceeded to co-opt tribal leaders by setting up the "Djema'a", a political institution loosely based on traditional Sahrawi tribal leaders. The "Djema'a" members were hand-picked by the authorities, but given privileges in return for rubber-stamping Madrid's decisions.