The Portuguese were the first Europeans to enter the region of present-day Uruguay in 1512. The Spanish arrived in present-day Uruguay in 1516. The indigenous peoples' fierce resistance to conquest, combined with the absence of gold and silver, limited their settlement in the region during the 16th and 17th centuries. Uruguay then became a zone of contention between the Spanish and Portuguese empires. In 1603, the Spanish began to introduce cattle, which became a source of wealth in the region. The first permanent Spanish settlement was founded in 1624 at Soriano on the Río Negro. In 1669–71, the Portuguese built a fort at Colonia del Sacramento.