Pedro de Mendoza was born in
Guadix, Grenada, part of a large noble family that was preeminent in Spain. He was the son of Fernando de Mendoza of Guadix and Constanza de Luján. His father was the grandson of
Íñigo López de Mendoza, 1st Marquis of Santillana. His family settled in Guadix after its
reconquest by the Christians in 1489. He was a page at the Spanish court of
Emperor Charles V and accompanied the sovereign on his trip to
England. In 1524 he received the title of knight of the
Order of Alcántara and later, through the influence of his father — the knight Fernando de Mendoza Guadix — entered the
Order of Santiago. He later fought in the
Italian Wars against the French, in which he participated in the
Sack of Rome in 1527. In 1529, he offered to explore South America at his own expense and establish colonies. Thanks to the efforts of his relative María de Mendoza, wife of Secretary of State
Francisco de los Cobos, in 1534 his offer was accepted: he was made
adelantado governor,
captain general, and
chief justice over
New Andalusia. This grant allowed him authority over as much land as he could conquer, within 200
leagues of the southern limit of
New Toledo. Although this was measured along the Pacific coast, it was understood that his efforts would be directed towards the
Río de la Plata on the Atlantic. The Emperor gave Mendoza 2000 men and 13 ships on the condition that within two years Mendoza should transport 1000 colonists, build roads into the interior, and construct three forts. He was to have half the treasure of the
chiefs killed and nine-tenths of the ransom. The office of Governor was also, in theory, made hereditary. That year, he set sail with a considerable fleet, but a terrible storm scattered it off the coast of Brazil. Here his lieutenant, Juan de Osorio, was assassinated, according to some authorities by the orders of Mendoza himself because of suspected disloyalty. Mendoza sailed up the Río de la Plata in 1535 and founded
Buenos Aires on 2 February 1536. Mendoza was not a very effective leader because he was debilitated by a severe case of syphilis. He spent half of his time ill in bed, but he put as much effort as he could into the expedition. No notable campaigns occurred in the River Plate during this time, and the only chronicler was a German soldier named
Ulderico Schmidt (or Ulrico Schmidl). Schmidt came over to the River Plate with Don Pedro and stayed there for eighteen years, fighting in almost every battle. His account of this early history of the River Plate region is the most important document from that time period. == Battling the natives along the Río de la Plata ==