Mahdia Crusade. The Mahdia Crusade (1390), also known as the Barbary Crusade or the Crusade of Louis II de Bourbon against Mahdia, was a Franco-Genoese military expedition in 1390 that led to the siege of Mahdia, a stronghold of the Barbary pirates. A work by Belgian court historian Jean Froissart called the "Chronicles of England, France, and the Adjoining Countries" (c. 1400), referred to as Froissart's Chronicles, includes an account of this crusade.