Wars of the Roses the Hundred Years' War, unfolding the structural problems of feudalism, combined with the mental infirmity and weak rule of King Henry VI which revived interest in Richard of York's claim to the throne. Historians disagree on which of these factors to identify as the main reason for the wars. With the Duke of York's death, the claim transferred to his heir, Edward, who later became the first Yorkist king of England, as Edward IV. He reigned from 1461, interrupted by a Lancastrian uprising and reinstallment of Henry VI in 1470 to 1471, until his sudden death in 1483. His son
Cham–Vietnamese War (1471) and once their economies recovered, these two kingdoms went to war again. When fighting resumed in 1471, the Champa kingdom found itself weakened and isolated. It has experienced numerous civil wars and, at one point, had five different rulers. For its earlier attack on Angkor, the Khmers ignored the Cham's request for assistance when Vietnam invaded. The Cham also requested Ming China to intervene by helping bring the Vietnamese back in line by force and demarcate the border between Champa and Vietnam. China, however, only verbally rebuked the Vietnamese for its incursion, which the Vietnamese ignored, proceeding with its attack