Philip IV (Spanish: Felipe Domingo Victor de la Cruz, Portuguese: Filipe III; 8 April 1605 – 17 September 1665), also called the Planet King (Spanish: Rey Planeta), was King of Spain from 1621 to his death and (as Philip III) King of Portugal from 1621 to 1640. Philip is remembered for his patronage of the arts, including such artists as Diego Velázquez, and his rule over Spain during the Thirty Years' War. By the time of his death, the Spanish Empire had reached approximately 12.2 million square kilometres (4.7 million square miles) in area, the largest empire in the world, but in other aspects was in decline, a process to which Philip contributed with his inability to achieve successful domestic and military reform. He was succeeded on his death by his young son Charles II as King of Spain and in 1640 (with the collapse of the Iberian Union) by John IV as King of Portugal.