It is a history book. The Ancien Régime (French pronunciation: Old or Former Regime) was the monarchic, aristocratic, social and political system established in the Kingdom of France from approximately the 15th century until the later 18th century ('early modern France') under the late Valois and Bourbon dynasties. The administrative and social structures of the Ancien Régime were the result of years of state-building, legislative acts (like the Ordinance of Villers-Cotterêts), internal conflicts and civil wars, but they remained a confusing patchwork of local privilege and historic differences until the French Revolution ended the system. Much of the medieval political centralization of France had been lost in the Hundred Years' War, and the Valois Dynasty's attempts at re-establishing control over the scattered political centres of the country were hindered by the Wars of Religion. Much of the reigns of Henry IV, Louis XIII and the early years of Louis XIV were focused on administrative centralisation. Despite, however, the notion of 'absolute monarchy' (typified by the king's right to issue lettres de cachet) and the efforts by the kings to create a centralized state, Ancien Régime France remained a country of systemic irregularities: administrative (including taxation), legal, judicial, and ecclesiastic divisions and prerogatives frequently overlapped, while the French nobility struggled to maintain their own rights in the matters of local government and justice, and powerful internal conflicts (like the Fronde) protested against this centralization.