She also writes that “he had two secret meetings with the Stanley’s.” This quote shows that Henry knew he needed the Stanley’s co-operation to attain the crown. If he did not believe this he would not have met the Stanley’s at all let alone in secret. More evidence corroborates this statement, “He had gathered a sizeable force, if by no means a large one.” This shows that Henry had an army but was not large like Richard III, so Henry would have been aware that the Stanley family had raised an army of 3000 Feudal Men-At-Arms and mounted Knights. This force could tip the balance if they were added to his army. Therefore it could be interpreted as Henry thought without more men he would lose to Richard so he met with the Stanley’s secretly (in secret to avoid declaring Stanley’s treachery in public and to keep Richard in the dark about his position). This shows that Henry owed his success to the support of the Stanley.
The Stanley family were a prominent noble family, they had vast estates in the north of England along with various peerages and titles. As well as being influential the Stanley’s were very wealthy due to the size of the area they controlled. The Stanley family were the second only to the King in the feudal system of northern England therefore they could call up a large army using the feudal allegiance system. Due to this the Stanley family were very useful if they allied with your forces. The Stanley’s had been loyal to Richard and fought along side him at Tewksbury but at Bosworth they dramatically switched sides (Sir William Stanley’s Knights killed Richard III at Bosworth). Henry knew that he who had the loyalty of the Stanley’s had the loyalty of Northern England. Also because Henry’s claim to the throne was so weak he would need influential families like to Stanley’s and also the Woodville's to stand by him and help him keep his throne from pretenders (Although Sir William Stanley was beheaded in 1495 for supporting a pretender). Henry’s army was outnumbered two to one by Richards army and only exceptional leadership and talent would carry the day, Henry had limited command and battlefield experience but Richard was a talented veteran, Henry had to recruit the Stanley’s into his army to try to even out the numbers. Also the Stanley’s wealth could be used to stabilize his position as King if he won the battle e.g. bribing noblemen into allegiance.
Overall the case of Henry VII owing his success in attaining the crown to the support of the Stanley’s is quite strong, they were not just a military force but a force with influence and wealth. So you could say without the support of the Stanley’s Henry would have lost his life by either being executed by Richard post-Bosworth or defeated in one on one combat with Richard on the field.
It would be very naive to say that there were not other reasons why Henry Tudor attained the crown in 1485, not just due to Stanley support, Henry’s support came from other place as well. The French king Charles XIII lent out thousands of French mercenary’s to Henry with the hope that Henry would become king and not threaten France with invasion. Although the Stanley’s provided an extra 3000 there were more than 3000 given by Charles. Also the Stanley’s were not the only aristocrats to support Henry, the Duke of Northumberland and Earl of Westmoreland are other examples. So as the majority of Henry’s force was not from the Stanley’s then it could be said that he did not completely owe his success to the support of the Stanley’s.
Although Richard III was an enemy of Henrys it could be argued that his action in terms of leadership of England caused Henry to attain the throne. Richard was unpopular with many social groups of England and he was even more unpopular with the aristocracy because he allegedly murdered his nephews and grabbed the throne, also he was very harsh when it came to loyalty, he beheaded the Duke of Buckingham in a privy council meeting for example, this was not a rare event, Richard had many other people put to death during his reign. Therefore Richard contributed to his own downfall because he treated the aristocracy poorly and many defected to Henry because they thought they could depose Richard III.
The Woodville’s were also very important in attaining the crown for Henry because by becoming betrothed to Elizabeth of York (a Woodville) Henry united the families of Lancaster and York and the nobles of England could see an end to the dynastic violence if Henry was victorious, also the Woodville's did not illegally gain power they legitimately married into the royal family and the Princes in the Tower were the true heirs to the throne so many of the nobles could see that although Henry aimed to usurp Richard he would bring England to a period of peace again.
Richard had also exiled many nobles for betraying him on way or another. Many of these nobles fled to the French court and as Henry Tudor was one of his exiles he gained the support of other noblemen who had been exiled. Each one of these noblemen could summon and armed force, an example is the Marquis of Dorset who had been exiled. This shows that Henry drew much of his support from the enemies of Richard and not just from the Stanley's.
Another deciding factor in Henry attaining the crown was that Henry was a Lancastrian and Richard was Yorkist many Lancastrians resented being ruled over by a Yorkist tyrant and would rather a Lancastrian was on the throne, therefore many diehard Lancastrians ignored Richards orders of loyalty and joined Henry further enhancing his opportunity to attain the throne.
Source 4 shows a number of factors which show that the Stanley’s were not a directly responsible for Henry Tudors ascension to the throne of England. The source writes, “ As for the number of captives, it was very great.” This shows that many of Richards men had been forced onto the field because they had been threatened if this wasn’t the case they would haven’t surrendered so readily, they would have fought to the death. Also it writes, “submitted themselves to Henry. Most of them would have done so at the beginning,” this corroborates my previous point that many of the Ricardian supporters on the field were only there because they had been forced there under pain of death. This shows that Richards action, of summoning men that weren’t committed to him to fight, was one cause of Henry Tudor attaining the crown.
To conclude, I believe that the Henry Tudor attained the crown of England not just to the support of the Stanley’s so I disagree with the question. The Stanley’s were the last cause in a long line of causes which brought Henry to the throne and caused Richard to lose it. The Stanley’s are looked upon as being the main cause, this may have been true at Bosworth but in the years leading up to it many other causes mounted up against Richard. Henry attained the throne from support from France, exiled Nobles, diehard Lancastrians, the Woodville's and also the Stanley’s. It would be wrong to say that the whole reason why Henry Tudor became Henry VII was because Stanley Knights killed Richard, yes , it did end the battle but it did not end the War and secure Henry’s position, these political alliances were formed months or years before Bosworth and without those political alliances Henry would not have even reached Bosworth and British history would have been very different to what we know it today.