The primary cause of the War of the Roses in England was the power struggle for the English throne between two rival factions: the House of Lancaster and the House of York. Both houses were branches of the Plantagenet family and had strong claims to the throne, leading to a series of dynastic conflicts. The war was exacerbated by political instability, weak leadership, and struggles over succession, particularly after the reign of King Henry VI, whose mental health issues ignited deeper rivalries. The conflict ultimately underscored broader social and economic tensions within England, culminating in significant shifts in power and governance.