King Philip III of Spain reigned from 1598 to 1621. He was the son of King Philip II and Anna of Austria. His rule is often characterized by a focus on peace and diplomacy, particularly through the signing of the Treaty of London in 1604, which ended hostilities with England. Philip III's reign also saw the decline of Spanish power, marked by economic difficulties and military challenges. He relied heavily on his favorite, the Duke of Lerma, to manage the government. Despite his efforts to maintain stability, his era is often viewed as a period of stagnation for the Spanish Empire.