Because of this, Somerset became distinctly unpopular at home. However, because he retained the king's favour, he maintained his prestigious position at court.
In June 1451, Bordeaux in France, and Gascony, were lost to the French. This was disastrous news for the English and the King, Henry VI, took the loss very badly. York in turn, was quick to blame Somerset for the disaster and, with support for the king and his adherents at such a low point (due mainly to English failings in France), York, decided to risk all and attempt to wrest control from the king by force of arms and arrest the Duke of Somerset, thus removing him from his position as the king's most senior advisor. Doubtless this move was not only inspired by York's fear for the conduct of the war in France, but also because he was equally fearful that Somerset might take over the very position that York felt was his own, that of the most likely heir to Henry in the absence of the king having any children of his own. Thus York, believing that he had more popular support than he actually had, sailed from Ireland and landed in North Wales, gathered his forces and travelled straight for London and the encounter at Blackheath.

The Wars of the Roses Begin
After York's release from custody, there then followed several years of relative peace. However, by the year 1453, the political storm clouds were once again gathering over the country. By this year, England's possessions in France had been almost lost as the disastrous Hundred Years War had all but come to an end . It was this - it is said - that brought about the first bout of madness in Henry VI. What form this illness took is not recorded, but it seems that it manifested itself in a form of paralysis. York, with the king incapacitated, was made protector of England and took the opportunity to seek revenge on his earlier enemies, namely the Duke of Somerset, who was sent to the Tower on a revised charge of treason (for his poor management of the war in France) in September 1453. The Earl of Salisbury, Richard Neville and his eldest son Richard, Earl of Warwick, also took the opportunity afforded by the king's illness and, under the cover of their kinsman's protectorate began to seek their revenge against the Percy family, the Earls of Northumberland, with whom, they had held a long running feud, over the issue of ownership of property in Northumberland and Yorkshire .

Thus, England was plunged into a series of minor wars between the land's most powerful lords to which the Duke of York, as protector was able to use his authority to the advantage of his family and supporters. However, this all came to an end when the king recovered from his illness in January 1455. Somerset was released from the Tower, and immediately formed a natural alliance with Henry Percy, Earl of Northumberland (and Percy's ally in the north Lord Clifford), against the Duke of York - who was stripped of his powers as protector - and his supporters, namely the Earl of Salisbury and the Earl of Warwick. With this the battle lines for the 'Wars of the Roses' were drawn. The pact between Somerset, Northumberland and Clifford, supported by the king would in later years go by the name of Lancastrians, taken from the family name of the House of Lancaster to which the lineage of Henry VI was derived. While the followers of the House of York, Warwick, Salisbury and the Duke of York himself became known as the Yorkists .