Cesare Borgia,  by Anonimous - Vienna, Kunthistorisches MuseumCesare Borgia

Cesare Borgia , or "Duke Valentino" was born in Roma in 1476 and died at Castello di Viana, Spain, in 1507. He was the illegitimate son of Cardinal Rodrigo de Borja, future Pope Alexander VI, with a Roman woman named Vannozza Cattanei. In addition to Cesare, Rodrigo and Vannozza had three other children, two boys ( Giovanni and Goffredo) and a famous daughter by the name Lucrezia Borgia,
Cesare was initially groomed for a Church career and was elevated by his father to the rank of Cardinal by the age of 22. From about this time, Cesare begins to be an active participants in Vatican politics. In 1494 Cesare accompanies Charles VIII of France on his descent on Naples where, later, in 1497, he will crown Frederick of Aragon king of Naples. In the meantime his elder brother Giovanni, who was in charge as captain general of the Church in its fight against the Orsini, allied with the French, was assassinated in mysterious circumstances. Part of the responsibility for the homicide fell on Cesare. The death of his elder brother, who was his father's favorite, meant that Cesare would consolidate his power. Firstly, he requested to be relieved of the Cardinalship —obtaining his wishes with a papal dispensation in 1498—in order to get into an advantageous marriage. In 1499 he married Charlotte d'Albret, a sister of the king of Navarre and lady-in-waiting at the court of Louis XII of France. Louis XII, in gratitude towards Cesare's father, Pope Aledander VI, for having granted him an annulment of his first marriage so that he could marry the widow of Charles VIII, made Cesare duke of Valentinois (Valence - hence the italianized title "Valentino"). From this time on Cesare became a man of Louis XII. He was him in his Lombardy expedition, and he was with him when Louis XII occupied Milan. Being so secure under French support, Duke Valentino conceived the idea of creating a new power in Italy with the design of founding a Borgia dynasty. Thus Cesare's aims were directed to subdue the territories northeast in the States of the Church (see Map). Though in theory subject directly to the pope, the rulers of these cities had been practically independent or dependent on other states for generations. Cesare Borgia hoped that by subduing them he would create a new central Italian kingdom that would rival Naples, Florence, Milan and Venice. In the seventh chapter of The Prince Machiavelli underscores the nepotistic aspect of the undertaking (see text, paragraphs beginning: Alexander VI, in wishing to aggrandize the duke, his son, had many immediate and prospective difficulties....), although the "effectual truth of the matter" may not be quite so. In any case, Cesare subdued the cities of Romagna one by one from 1499 to 1500. Made duke of Romagna by the Pope (1501), Cesare also seized Camerino, and the duchy of Urbino. He crowned his achievements by artfully luring his chief enemies to the castle of Sinigallia, where he had Vitellozzo Vitelli and Oliverotto da Fermo strangled on the spot. The rest were strangled in the same way a few days later at Città della Pieve. We have a very vivid account of this episode in the relation by Machiavelli—who had been sent by the Florentine Republic in a mission to Cesare Borgia—by the Italian title Del modo tenuto dal duca Valentino nell' ammazzare Vitellozzo Vitelli, Oliverotto da Fermo, il signore Pagolo e il Duca di Gravina Orsini presented here in English translation.
By killing his enemies, influencing the college of cardinals, pushing his conquests as far and as fast as possible, by ingratiating to and buying the loyalty of the Roman nobles, he had hoped to make his position as independent as possible of the Pope's control. But in August of 1503 Alexander VI died, and Cesare himself was struck by the same illness that killed his father. Cesare recovered and started maneuvering to make sure that the election of a new Pope would at least not be contrary to him. The new elected Pope was Pius III. Unfortunately he lasted only one month! The new Pope was Julius II, Giuliano della Rovere, an implacable enemy of both Alexander VI and Cesare Borgia. Also, Cesare Borgia's political construction was too weak. He had not killed all his enemies, who were waiting for the opportune moment to regain the possessions that Cesare had taken from them. Guidubaldo da Montefeltro returned to Urbino, the da Veranos reconquered Camerino, Giovanni Sforza regained Pesaro, and Pandolfo Malatesta returned to Rimini.
In the meantime Cesare Borgia was arrested twice, in Rome and in Naples, and in August of 1506 he went to Spain, but is again arrested.Finally on October 25 Cesare succeeded to escape and went to Pamplona finding refuge at the court of his brother-in-law, the king of Navarre. He died at the age of 32, on march 12, 1507, fighting for the king and against his insurgent vassals during the siege of the Castle of Viana.