“In reality, the Battle of Agincourt probably resulted in a lot of the political upheaval in England which lead to the War of the Roses. However, from a military point of view, it marked a major turning point the history of warfare and this is true REGARDLESS of how outnumbered the English were.”
The War of the Roses (actually a series of seperate conflicts) began long before Agincourt, when Henry Bolingbroke, Duke of Lancaster, deposed his incompetent cousin Richard II in 1399, his son was Henry V, and he probably sought glory in France to better secure his position at home from the Rival House of York. Henry V’s son Henry VI was an infant when he came to the throne, and proved to be weak and ineffectual, kept on the throne by his powerful regents and the inflence of his Queen, Margaret of Anjou. Until he was captured and eventually executed after the death of his only son and heir at the Battle of Tewkesbury in 1471....
You're absolutely right, I think I phrased it wrong. What I meant was that Henry V and the other Lancasters, in seeking glory in France, allowed the Yorks to regain power bases in England.
Henry V's father, John of Gaunt was arguably the de facto king of England during most of Richard II's reign. When John of Gaunt died in 1399 Richard II tried to claim his property, this made Bolingbroke hate him even more (Richard II had exiled Bolingbroke a few years before and John of Gaunt went along with it to maintain stability in England). Bolingbroke used this as his reason to seize control, though he probably had always planned to do this as soon as his father died.