D'Annunzio was a precocious talent who was recognised early in life and received an early education at the University of Rome. A prolific writer, his novels in Italian include Il Piacere (The Child of Pleasure, 1889), Trionfo della Morte (The Triumph of Death, 1894), and Le Vergine delle Rocce (The Virgin of the Rocks, 1896). D'Annunzio also wrote a number of plays in French, including Le martyre de Saint Sébastien (The Martyrdom of St Sebastian, 1911). He wrote the screenplay to the early motion picture Cabiria based on episodes from the Second Punic War. D'Annunzio's literary creations were strongly influenced by the French Symbolist school, and contain episodes of striking violence and depictions of abnormal mental states interspersed with gorgeously imagined scenes.
On September 12, 1919, he led the seizure by Italian nationalist irregulars of the city of Fiume, now Rijeka in Croatia, forcing the withdrawal of the inter-Allied (American, British and French) forces occupying the city. The plotters sought to have Italy annex Fiume, but Italy refused, and then began a blockade of Fiume demanding that the plotters surrender. D'Annunzio then declared Fiume an independent state, and began to support his claimed state through acts of piracy.
He coauthored with anarcho-syndicalist Alceste de Ambris the Carta del Carnaro, a constitution for Fiume. De Ambris provided the legal and political framework, to which D'Annunzio added his skills as a poet. De Ambris was the leader of a group of Italian seamen who had mutined and then given their vessel to the service of D'Annunzio. The constitution established a corporatist state, with nine corporations to represent the different sectors of the economy (workers, employers, professionals), and a tenth (D'Annunzio's invention) to represent the "superior" human beings (heroes, poets, prophets, supermen). The Carta also declared that music was the fundamental principle of the state.
D'Annunzio was associated with Benito Mussolini, and his method of government in Fiume, with large emotive nationalistic public rituals, blackshirted followers and strongarm repression of dissent, was in many ways a forerunner of Mussolini's methods.
D'Annunzio attempted to organize an alternative to the League of Nations for (selected) oppressed nations of the world (such as the Italians of Fiume), and sought to make alliances with various separatist groups throughout the Balkans (especially groups of Italians, though also some Slavic groups as well), although without much success.