Cabeza de Vaca had taken into his alliance the _Guaranís_, and with them he proceeded to attack another tribe, the _Guaycurùs_, on the opposite side of the river. These were, as might be expected, disconcerted at the sight of his armed horses and riders, and readily consented to be his allies. With their aid he prepared to follow the course of exploration towards _Peru_; and whilst vessels were being constructed for river navigation, he sent Irala forward with an expedition by land. Soon following in person and passing a settlement on the _Paraguay_, called _Puerto de los Reyes_, which had been founded by Irala, he penetrated into the interior; but from the want of provisions he had to return to _Paraguay_. There he and his people suffered to the full the hardships incident to the life of explorers. Whilst they were reduced by hunger, prostrated by fever, and tormented by mosquitoes, they were attacked by formidable bands of natives, having defeated whom, the _Adelantado_ was glad to turn his face again towards _Asuncion_. On his arrival, however, fresh troubles awaited him. During his absence a conspiracy had been hatched. His person was seized and his authority usurped, Irala being proclaimed governor in his stead. After a captivity of eleven months Cabeza de Vaca was sent a prisoner to Spain, in company with two official persons who were to prefer groundless charges against him; yet, notwithstanding his innocence and his services, he had, like Warren Hastings at a later period, to await during eight years a sentence of acquittal.