Alfonso I Este, duke of Ferrara (1476-1534) was a pro-French Italian leader who managed to maintain his position in the Po valley despite the hostility of a series of popes.
Alfonso was the son of Ercole I, duke of Ferrara from 1471. He inherited a generally pro-French policy from his father, but the family also had to watch their intermittently powerful Papal southern neighbours. In 1501 Alfonso was married to the infamous Lucrezia Borgia, the daughter of Pope Alexander VI (Rodrigo Borgia). At first Alfonso refused to associate with his new wife, but after the death of her father in 1503 and the defeat of her brother Cesare, Lucrezia settled into her new role. Under her management the court of Ferrara became a centre of the arts and letters.
In 1505 Alfonso inherited Ferrara, which was held from the Pope, as well as Modena and Reggio, which were originally Imperial territory. Alfonso had to defeat a plot to overthrown him led by his brother Ferrante and stepbrother Giulio. Once he was securely in control of his duchy he embarked on a military career.
He took part in the anti-Venetian War of the League of Cambrai (1508-1510). During this conflict he won a naval battle at Polesella, and recaptured the Polesine of Rovigo (an area north-east of Ferrara that had been lost by his father).
In 1510 Pope Julius II withdrew from the anti-Venetian League of Cambrai and began to form a new anti-French Holy League. During the resulting War of the Holy League (1510-1514) Alfonso lost control of Modena (1510) and Reggio (1512) and was excommunicated. He played a part in the brilliant French victory at Ravenna (11 April 1512), where his carefully controlled artillery hit the Spanish infantry in their trenches. This helped trigger a Spanish cavalry attack that was repulsed and helped clear the way for the French infantry to attack the Spanish lines.
Alfonso continued to have problems with the Pope, and in particular with the Medici Popes Leo X (reigned 1513-1521) and Clement VII (reigned 1523-1534). Both wanted to take the last of the Este lands. Pope Leo originally demanded the freedom to move against Ferrara while deciding whether to support Francis I of France or the Emperor Charles V. The Emperor was willing to grant that freedom, and in May 1521 the Pope came to an agreement with him, but later in the same year he died before he could act upon it. The same year also saw Alfonso suffer a minor battlefield defeat, part of the successful Imperial campaign that forced Odet de Foix, count of Lautrec, to abandon Lombardy.
Clement was even less successful. In 1523 Alfonso regained control of Reggio, and Modena followed in 1527. In 1526 Alfonso abandoned his normal pro-French stance and instead sided with Charles V. This helped win Charles the time he needed to reinforce his army in northern Italy, but funds were very limited. The army was almost out of control, but enough money was found to allow it to move towards Rome. In May 1527 the Imperial army attacked and sacked Rome, shocking Catholic opinion across Europe.
In the confusion after the sack of Rome Alfonso was able to recapture Modena. Alfonso soon changed sides again, and was back in the French camp by the time Clement came to terms with Charles in November 1527. His position was thus endangered by the virtual collapse of the French position in Italy after the failed siege of Naples of 1528, but he was eventually protected by Charles. In the treaties that ended the Second Hapsburg-Valois War the status of Modena and Reggio was left for Charles to decide later. Charles also created a League of the Italian powers, although Alfonso wasn't allowed to join until he was reconciled with Clement. The Emperor eventually officially awarded Reggio and Modena to Alfonso on 21 April 1531.
By the time of his death in 1534 he had thus regained control of his original inheritance, and it remained intact until the death of his legitimate grandson Alfonso II in 1597.
Alfonso had both legitimate children and illegitimate children with his mistress Laura Eustochia Dianti. His legitimate son Ercole II followed him as duke of Ferrara, and was succeeded in his turn by Alfonso's grandson Alfonso II. Alfonso II had no legitimate children. Pope Pius blocked the succession of Alfonso and Laura's descendents at Ferrara, but their descendent Cesare (1562-1628) did inherit Modena and Reggio.