From the late 12th century, an organized Lithuanian military force existed; it was used for external raids, plundering and the gathering of slaves. Such military and pecuniary activities fostered social differentiation and triggered a struggle for power in Lithuania. This initiated the formation of early statehood, from which the Grand Duchy of Lithuania developed. The disparate Lithuanian tribes along the Nemunas were united into the Lithuanian state by 1219, at the latest. The only Lithuanian Roman Catholic king, Mindaugas, was baptised as a Roman Catholic in 1251 and crowned as King of Lithuania on 6 July 1253.