sentences:  The Bastille continued to be used as a prison and a royal fortress under both Henry IV and his son, Louis XIII.When Henry clamped down on a Spanish-backed plot among the senior French nobility in 1602, for example, he detained the ringleader Charles Gontaut, the Duke of Biron, in the Bastille, and had him executed in the courtyard.Louis XIII's chief minister, Cardinal Richelieu, is credited with beginning the modern transformation of the Bastille into a more formal organ of the French state, further increasing its structured use as a state prison.