the Guaycuruans retained their control of the Chaco and gradually acquired horses, a taste for Spanish beef, and iron weapons and tools. In the 17th century, Guaycuruan raids forced the abandonment of Concepción del Bermejo, Argentina and the relocation of Santa Fe, Argentina. In retaliation, in 1677, the Spanish massacred 300 Mbayan traders who were camped near Asunsción. By the early 1700s, bands of up to 400 Guaycuruan warriors were attacking Spanish settlements in Tucuman and other nearby Argentine provinces. Their raids forced the Spanish to abandon some frontier areas. Frequent Spanish military expeditions against the Guaycuruans were only temporarily successful if at all. The Guaycuruans largest raid came in 1735 when 1,000 Mocobis and Tobas descended upon Salta Province, Argentina. They killed or captured hundreds of people, ransoming some captives and keeping others as slaves, and much livestock. Mbaya raids in Paraguay during the same decade resulted in the death of 500 Paraguayans and the theft of 6,000 head of livestock. However, Guaycuruan power had reached its zenith. A smallpox epidemic from 1732 to 1736 killed many, especially Mocobis; Spanish settlements were encroaching on the Chaco, and some of the Guaycuruans were adopting Spanish culture and religion. Moreover, the human pressure on the Chaco led to its environmental deterioration and it became less suitable as a habitat for the traditional hunting-gathering culture plus horse and cattle herds of the Chaco peoples. Jesuit missionaries made unsuccessful attempts to establish missions or reductions among the Guaycuruans in the early 1600s. Their first successful mission was established among the Mocobis at San Javier, north of Santa Fe, Argentina in 1743. Several other missions were established among the various ethnic groups of the Guaycuru and the mission population reached a peak of 5,000 to 6,000 in the early 1780s. The population of the missions was unstable as many Guaycuruans returned to their nomadic ways after a residence at a mission. Many Guaycuruans were also, by this time, integrated into the Spanish economy, raising livestock, growing crops, and working for wages--although many also continued smuggling and stealing livestock and remained hostile to the Spanish. Decline By the early 19th century, when the South American countries sought independence from Spain, the Guaycuruan peoples were divided among those who lived in missions and were at least partially integrated into Hispanic and Christian society and those who continued to live as nomads in the more isolated parts