Mapuches used both individual digging sticks and large and heavy trident-like plows that required many men to use in agriculture. Another tool used in agriculture were maces used to destroy clods and flatten the soil. The Mapuche canoes or "wampus" were made of hollow trunks. In the Chiloé Archipelago another type of watercraft was common: the "dalca". Dalcas were made of planks and were mainly used for seafaring while wampus were used for navigating rivers and lakes. It is not known what kind of oars early Mapuches presumably used. The Spanish expansion into Chile was an offshoot of the conquest of Peru. Diego de Almagro amased a large expedition of about 500 Spaniards and thousands of yanaconas and arrived at the Aconcagua Valley in 1536. From there he sent Gómez de Alvarado south in charge of a scouting troop. Alvarado reached the Itata River where he engaged in the Battle of Reynogüelén with local Mapuches. Alvarado then returned north and Diego de Almagro's expedition returned to Peru since they had not found the riches they expected. Another conquistador, Pedro de Valdivia, arrived in Chile from Cuzco in 1541 and founded Santiago that year. In 1544 captain Juan Bautista Pastene explored the coast of Chile to latitude 41° S. The northern Mapuche, better known as Promaucaes or Picunches, unsuccessfully tried to resist the Spanish conquest. Northern Mapuche groups appear to have responded to the Spanish conquest abandoning their best agricultural lands and moving to remote localities away from the Spanish. In this context one of the reasons the Spanish had to establish the city of La Serena in 1544 was to control Mapuche groups that had begun to migrate north following the Spanish founding of Santiago. The Spanish understood this abandonment as an attempt to have them leave Chile much in the way Diego de Almagro did in his failed expedition of 1535–1537. According to chronicler Francisco de Riberos northern Mapuche put cultivation on hold for more than five years. 17th century Jesuit Diego de Rosales wrote that this was a coordinated strategy that was decided by a large assembly of many tribes. The Spanish found themselves in great distress as a result of a lack of supplies, but ultimately this strategy was unsuccessful in forcing Spanish conquerors out of Central Chile.