Naples At the end of 1518, Isabella planned to travel to Poland to visit her daughter, who was in the last stages of her first pregnancy. However, the Duchess did not arrive due to the death of her aunt, Dowager Queen Joanna of Naples, on 27 August of that year. Joanna bequeathed a large fortune to Isabella, which in part also belonged to King Charles I of Spain. In order to take over her aunt's bequest, the Duchess had to apply to the highest Neapolitan court. She asked for help from her son-in-law, who sent his secretary, Jan Dantyszek, to Spain. By helping Isabella, Sigismund I hoped that Bona Maria's dowry would be paid out sooner if the trial was won. When the matter was not settled, the Polish King sent to King Charles in April 1520 another ambassador, Hieronymus Łaski, but this mission also ended in failure. The opportunity to clarify the matter came when Dantyszek was to go directly to see Charles I. On the way, the royal secretary stopped in Spain, where on 24 February 1523 he discussed the inheritance of Isabella with Chancellor Gattinara. In July 1523, Sigismund I sent his secretary, Ludwik Decjusz, to Isabella, to help her in resolving the ongoing conflict. Death During her last years, Isabella saw her daughter become a mother to four of her six children: Isabella (born 18 January 1519; by marriage Queen of Hungary and Croatia), Sigismund Augustus (born 1 August 1520; later King of Poland and Grand Duke of Lithuania as last male monarch from the Jagiellonian dynasty), Sophia (born 13 July 1522; by marriage Duchess of Brunswick-Lüneburg) and Anna (born 18 October 1523; later Queen regnant of Poland and Grand Duchess regnant of Lithuania, and by marriage Princess of Transylvania). Not giving up on uniting the rival branches of the Sforza family, Isabella sent envoys to Poland to propose marriage of her eldest granddaughter, the younger Isabella, to Francesco II Sforza, newly installed Duke of Milan. However, Sigismund I refused as Milan was contested and Francesco II's hold was tenuous. Isabella didn't live long enough to see the resolution of her aunt's inheritance. At the beginning of October 1523 she fell seriously ill. In early February 1524, the disease worsened and the Duchess died a few days later, on 11 February, aged 53. Initially buried in Bari, her remains were returned to Naples and buried in