The Amazon Basin and some large adjoining regions had been considered Spanish territory since the Treaty of Tordesillas and explorations such as that by Francisco de Orellana, but Portugal fell under Spanish control between 1580 and 1640. During this time, Portuguese territories in Brazil were controlled by the Spanish crown, which did object to the spread of Portuguese settlement into parts of the Amazon Basin that the treaty had awarded to Spain. Still, Luis Jerónimo de Cabrera, 4th Count of Chinchón sent out a third expedition to explore the Amazon River, under Cristóbal de Acuña; this was part of the return leg of the expedition of Pedro Teixeira.