The period of civil war called the Wars of the Roses is traditionally viewed as lasting from 1455 to 1485, from Richard, Duke of York's attempt to unseat King Henry VI until his own son, King Richard III was defeated at Bosworth. In reality, the roots of this conflict lay long before it erupted. As the large and ambitious royal family created by King Edward III began to feud and squabble, trouble moved ever closer. As unpopular as King Richard II was, his removal in favour of his cousin broke a line of male succession that stretched back 300 years to King Henry II. Unseating God's anointed King of England was previously unthinkable. Henry Bollingbroke made it an option, a choice in the face of poor kingship. He opened a door through which his own grandson was to be pushed, dragging a bickering nobility and a terrified country with him.
Ultimately, King Henry VI's weak rule, his strong willed wife Margaret of Anjou and the couple's preferment of the Beaufort Dukes of Somerset was to set the country on a course so reminiscent of the removal of King Richard II that Henry's own removal must have seemed not only feasible but desirable. Richard, Duke of York's handling of the matter was initially applauded. His Protectorate was a time of even handed peace. Yet by the end of the 1450's he had lost control of the situation, but had travelled too far to stop. His son was to complete his work, yet not fully for over a decade more, hauling the country through more uncertainty and bloodletting.
King Richard III may have truly believed that his duty required him to take the throne or he may have perceived a situation so threatening to him that he had to act, but once more the removal of a king seemed an option rather than a sin. Unable to reconcile parts of the country to his rule, some of the most crucial and powerful parts, Richard lost his Crown to the unlikeliest of kings, Henry VII, who arrived with little hope yet played the game better than Richard had, recognising the need to attract the support of those who could win him the Crown. In him, latent Lancastrian hope and disaffected Yorkist hearts found a welcome home and he used this to unseat another king, the fourth removal of a monarch in under a hundred years. His success lay in his understanding and manipulation of the winds of politics.
Neither did the War of the Roses end conclusively at the Battle of Bosworth in 1485. The last pitched battle was to take place two years later at East Stoke and pretenders were to constantly harass Henry VII in the name of the White Rose. Even Henry VIII was so terrified of the faction that he at least believed plotted against him, whether it did in truth or not, that executions based solely upon Yorkist blood were still taking place in 1540's with Reginald Pole at least evading him until after that king's own death.
It is also worth considering the impact of small, local feuds. Many of these were settled under the guise of the war for the Crown. Many were to decide loyalties or push men of power from or toward one side or another, frequently dependent upon which side best served their own interests. Warwick is remembered as the Kingmaker, but he was only the most powerful of many seeking to improve their own lot or right wrongs, perceived or real.
The Wars of the Roses is a fascinating era that has contributed to the defining of England, not least because it placed the Crown finally upon the head of first of the Tudors who were to remake England in ways both positive and negative. The amount of subtle political manoeuvring and careful placement of alliances both within England and abroad by those hoping to influence or destabilise for their own ends is infinitely fascinating and seems to force people to take a side, even now.
This period of English history is supremely summed up by George R.R. Martin in his Song of Fire and Ice series of novels: "When you play the game of thrones, you win, or you die." For so many during this period, that was a fact of everyday life.
Bosworth: Birth of the Tudors, Chris Skidmore (W&N)
The History of England Volume 1: Foundation, Peter Ackroyd (Pan Books)
Lancaster & York: The Wars of the Roses, Alison Weir (Vintage)
Blood Sisters: The Women Behind the Wars of the Roses, Sarah Gristwood (Harper Press)