Write a question about the following article: With John of Lorraine dead, René appointed John's eldest bastard son, John of Calabria, Count of Briey, his new lieutenant. In 1471 the French troops fighting with the Catalans retired to France and the advantage shifted decidedly to John II. Joan Margarit, the Bishop of Girona, returned his city to John , followed by other towns. Duke John of Lorraine died at Barcelona on 16 December 1470 and the Catalans lost their most important ally. King René lived until 1480, but was not personally present in Catalonia. King John II campaigned in the Alt Empordà until June 1472 and then against Barcelona. A naval and land siege lasted from November 1471 to 16 October 1472. By the Capitulation of Pedralbes, Barcelona surrendered to king John, John agreed to let the warchief John of Calabria leave peacefully and a general pardon was granted. The Count of Pallars, however, was not pardoned. The acts of the Consell and the other organs of Catalan government since the death of Charles of Viana were approved and John swore to uphold the Constitucions. The Capitulation of Vilafranca, however, was rejected.

Question about the article:
How many years was John II's siege on Barcelona?