Wars of the Roses
Wars of the Roses were a series of battles in 15th century England in which the houses of York and Lancaster vied for posession of the throne. The wars were so called because both houses used a rose in their arms: a red rose for the house of Lancaster, and a white rose for the house of York.
There is also a medieval urban legend that the other noble houses declared their allegiance by picking roses in the garden of the Temple in London. It is unlikely but vaguely possible, given English eccentricity.
The Battle of St. Albans
In 1455, Richard, the Duke of York claimed that the Lancastrian King Henry VI had no right to the throne, as his grandfather Henry IV had seized the crown by force in 1399. Followers of the Duke succeeded in deposing Henry and installing Edward IV for a time but Henry regained the throne and held it until 1471.
The Battle of Tewkesbury
In 1471, Edward succeeded in regaining the throne, and the Yorkists held power through the reign of Richard III
The Battle of Bosworth
In 1485, Henry VII took the throne from the Yorkists, claiming descent from two junior houses of Lancaster. He effectively ended the conflict by marrying into the house of York, thus uniting the two factions. This was the beginning of the powerful Tudor dynasty.