failure when Cabot and Diego García made their next attempt to find the Sierra de la Plata. The local indigenous people took advantage of their absence to attack and destroy Fort Sancti Spiritu, killing many of his men. Low on morale, food, and supplies, Cabot and his crew were finally forced to give up their goal and return to Europe. Pedro de Mendoza In 1534, King Charles I authorized Pedro de Mendoza to "conquer and populate the lands and provinces around the Solís River, which some call the Plate". With fourteen ships and some 1,200 men, it was at the time the largest and most important expedition that had left Europe for America. In 1536 Pedro de Mendoza founded the port of Santa María de los Buenos Ayres, which was probably located in what is now the Parque Lezama in Buenos Aires. Resources were in short supply to support such a population, and after the Spaniards mistreated the local Querandís, they stopped supplying food to the settlement. Mendoza decided to send out two fleets in search of food: the first, led by his nephew Gonzalo de Mendoza, headed toward Brazil, and the second, led by Juan de Ayolas, went up the River Paraná with three ships and 270 men. Meanwhile, Mendoza ordered his brother Diego to take 300 soldiers and 30 cavalrymen to fight the Querandís. The battle was a failure. Diego de Mendoza was killed, and the Querandís began a long-lasting siege of Buenos Aires. Cut off from supplies, the settlers began to eat their horses and their dead. Finally, the Querandís withdrew, and in a few days, the Juan de Ayolas expedition returned with the news that they had managed to build a fort called Corpus Christi upriver near the modern-day town of Gaboto and had encountered some indigenous people who talked about the Sierra de la Plata. Pedro de Mendoza decided to travel to the fort with Ayolas and some 400 men. During the voyage, some 200 men died of sickness and hunger, and once they reached Corpus Christi, Mendoza consulted Cabot's map to find that they were still far from their destination. These major setbacks, along with the syphilis he had contracted, convinced Mendoza to return to Europe after a short stop in Buenos Aires. Pedro de Mendoza died on the open sea on June 23, 1537. Juan de Ayolas, who had left Corpus Christi on