 On 25 April 1443, at the age of sixteen, in a ceremony in Siena the Pope Eugene IV made him Duke of Urbino as a reward for his support in the war against the Sforza in the Marche.Oddantonio exhausted the treasury of the small state with his excessive lifestyle (he is reported to have held extravagant parties, some lasting over 15 days), and consequently had to exert heavy taxes over the duchy.He also sought the support of their arch-enemies, the Malatesta, seemingly reaching a complete independence from them.