Tilly focused his attention on Europe after the decline of the Roman Empire. During this period, state organization was mostly informal and the work of local lords who controlled relatively small areas. Peasants gave up revenue in order to benefit from the security and protection offered by a powerful local lord. Over time, these feudal lands consolidated and required bigger armies in order to offer protection from both internal and external threats. Larger armies proved more effective and subsequently, more money was needed to pay these armies. Feudal lands continued to develop and combine into larger kingdoms ruled by kings. Kings then demanded money in the form of taxes. To impose these taxes, they required a protocol for counting and enforcing collections, so they set up formal state institutions.