either of two civil wars in 13th-century England. The First Barons' War (1215–17) was precipitated by King John's failure to observe the terms of Magna Carta: many of the Barons'grievances were removed by his death (1216) and peace was concluded in 1217. The Second Barons' War (1264–67) was caused by Henry III's refusal to accept limitations on his authority: the rebel Barons (led (1264–65) by Simon de Montfort), initially successful, were defeated at the battle of Evesham (1265); sporadic resistance continued until 1267