Sebastian was King of Portugal for 21 years in the 16th Century. He came to the throne young and lost his life on Crusade.

He was born on Jan. 20, 1554 in Lisbon. His father was John, the crown prince, and his mother was Princess Joana of Spain. John died shortly before his son was born, and Joanna wasn't long in the country, traveling to Spain to serve as regent for her father, Charles I, and then her brother, Philip II. She never saw her son again.

Stepping in to serve as regent were Sebastian's grandmother, Catherine of Austria, and then his great-uncle, Cardinal Henry of Évora. The reigning monarch was the baby's grandfather, King John III. The king named his grandson as his heir and, when the king died, on June 11, 1557, young Sebastian became king.

Tutor to the young king was Aleixo de Meneses, who had served in the same role with Sebastian's father. Sebastian also gained an education from the religious order the Jesuits and decided that he would embark on a religious Crusade to drive Muslim forces from North Africa. He wanted to so much to expand the Catholic faith that he sent a large sum of money to France's Charles IX to aid in his fight with the Huguenots.

Sebastian had assumed his own rule in 1568 and, a decade later, found his chance to invade North Africa, after the pope gave him official sanction to conduct a Crusade. Taking advantage of a succession dispute, Sebastian cobbled together a multinational force and waded into the fight, in what became known as the Battle of the Three Kings. (The Muslim rulers, Abd-al-Malik and Abu Abdullah Mohammed II, weren't technically kings.) Another name for this struggle is the Battle of Alcáccer Quibir. This was on Aug. 4, 1578. The combined forces of Sebastian and Abdullah Mohammed were 23,000; facing them was an army of 60,000. The Portuguese forces were routed, and all three rulers who fought lost their lives. Sebastian was reportedly last seen riding straight into enemy lines.

Before he left, Sebastian was considering three offers of marriage, one to wed the daughter of King Philip II of Spain, one to marry the daughter of Emperor Maximilian II, and the third to wed the daughter of Queen Catherine of Medicis of France. Sebastian had not made up his mind before he went off on Crusade, so he was not married when he went. Further, he had had no children and so had no clear succession lined up. Taking the throne in this vacuum was Cardinal Henry, Sebastian's great-uncle and former regent, who became King Henry.

During his short reign, Sebastian established two hospitals in Lisbon to care for victims of the plague, an outbreak of which occurred in 1569. The king also established laws for the military. During his reign, Portugal expanded its overseas possessions, claiming control of territory in what are now of Angola, Mozambique, and Macau.