Named for its mythical leader “Captain Rock,” avenger of agrarian wrongs, the Rockite movement of 1821–24 in Ireland was notorious for its extraordinary violence. In Captain Rock, James S. Donnelly, Jr., offers both a fine-grained analysis of the conflict and a broad exploration of Irish rural society after the French revolutionary and Napoleonic wars.     Originating in west Limerick, the Rockite movement spread quickly under the impact of a prolonged economic depression. Before long the insurgency embraced many of the better-off farmers. The intensity of the Rockites’ grievances, the frequency of their resort to sensational violence, and their appeal on such key issues as rents and tithes presented a nightmarish challenge to Dublin Castle—prompting in turn a major reorganization of the police, a purging of the local magistracy, the introduction of large military reinforcements, and a determined campaign of judicial repression. A great upsurge in sectarianism and millenarianism, Donnelly shows, added fuel to the conflagration. Inspired by prophecies of doom for the Anglo-Irish Protestants who ruled the country, the overwhelmingly Catholic Rockites strove to hasten the demise of the landed elite they viewed as oppressors.     Drawing on a wealth of sources—including reports from policemen, military officers, magistrates, and landowners as well as from newspapers, pamphlets, parliamentary inquiries, depositions, rebel proclamations, and threatening missives sent by Rockites to their enemies—Captain Rock offers a detailed anatomy of a dangerous, widespread insurgency whose distinctive political contours will force historians to expand their notions of how agrarian militancy influenced Irish nationalism in the years before the Great Famine of 1845–51.