Portuguese America occupied the highest priority in John's administration of the Portuguese Empire. The American colonies of Brazil and Maranhão had become vital sources of wealth to the royal treasury, making the protection, expansion, and good governance of Portuguese America crucial to imperial policy in the Joanine era. Expansion of Portuguese territory in the Americas was also a concern, which was primarily achieved through military incursions into the interior of the continent by "Bandeirantes". Portugal also regained control of Uruguay following the Treaty of Utrecht, in 1714, and successfully defended it against an attempted Spanish reconquest in the Spanish–Portuguese War of 1735–37.