He was born in
Trujillo, in the province of
Extremadura, the son of Gutiérrez de Sotomayor e Hinojosa and Beatriz de Valmediano. At the age of 15 he joined the army, serving first in
Italy until 1567, and then moving to
In 1580 he was called back to
Madrid by his official duties.
King Philip II, seeing his military record, awarded him a knighthood in the
Order of Santiago and sent him on a campaign against
Portugal. However, at that time news arrived from
Chile, where the
Arauco War continued and reinforcements were needed. The king subsequently decided to name Sotomayor governor of the district and send him there with a large contingent of soldiers to resolve the situation.