Velázquez quickly commissioned Francisco Hernández de Córdoba to lead an expedition which sailed in February, 1517, with instructions to explore certain neighboring islands. They soon came upon the shore of what they initially believed to be a large island, thus marking the Spanish discovery of the Yucatán Peninsula. Initial encounters with the Mayans living along the coast turned into armed conflict; 25 Spaniards were killed and many more wounded, including Córdoba himself. On his return to Cuba, Córdoba reported to Velázquez that the Mayans exhibited a sophistication not seen before in the region, including buildings of stone and mortar, clothing of woven cloth, and ornamentation of gold and silver.