Henry VII, the first Tudor king, claimed the English throne through his mother, Lady Margaret Beaufort. Margaret was a descendant of John of Gaunt, the third surviving son of King Edward III, through an illegitimate line. Although this made Henry's claim somewhat tenuous, he was able to bolster it through a combination of political maneuvering, military force, and luck.

Henry's main rival for the throne was Richard III, who had seized power in 1483 following the death of his brother, King Edward IV. Richard was widely suspected of having played a role in the disappearance of Edward's two young sons, who were next in line for the throne, and his reign was marked by controversy and unrest.

Henry spent several years in exile in France, Brittany, and later in the court of the Duke of Burgundy, gathering support and planning his invasion of England. In 1485, he landed in Wales with a small army and marched eastward to meet Richard's forces at the Battle of Bosworth Field.

Henry VII's preparations for his invasion of England were extensive and carefully planned. He spent several years in exile in France and Brittany, where he sought support from the French king, Charles VIII, and from other exiled Lancastrians. He also made an alliance with the Duke of Brittany, who provided him with troops and ships.

In August 1485, Henry set sail from Brittany with a fleet of around 200 ships and an army of between 2,000 and 5,000 men. He landed at Milford Haven in Wales on August 7, where he was met by Sir Rhys ap Thomas, a powerful Welsh landowner who had pledged his support to the Lancastrian cause.

Henry and his army then marched eastward, gathering support as they went. Many Welshmen joined Henry's army, and he also received support from the Stanleys, a powerful family in the north of England who had been allies of the Lancastrians during the Wars of the Roses.

Henry's army grew as he marched, and by the time he reached Leicester on August 20, he had an army of around 5,000 men. He then moved on to Bosworth Field, where he met the forces of King Richard III.

During the battle, Henry's forces were initially at a disadvantage, but they were able to gain the upper hand when Lord Stanley, who had initially declared for Richard, switched sides and brought his forces over to Henry's side. Richard was killed in the battle, and Henry was crowned King of England on August 22, 1485.

Henry's success at Bosworth was due in large part to the support he was able to generate once he had landed in Wales. His alliance with the Duke of Brittany and his support from the French king allowed him to amass a large army and fleet, and his careful planning and preparation allowed him to land successfully in Wales and begin his march eastward.

Once he had landed, Henry was able to gain the support of Welsh and English nobles who were disaffected with Richard III's rule. The support of the Stanleys was crucial to his victory at Bosworth, and their defection to his side was likely the result of a combination of factors, including their long-standing alliance with the Lancastrians and the promise of rewards from Henry.

The Battle of Bosworth was the culmination of a long and complex series of events that began with the Wars of the Roses, a series of civil wars fought between the houses of York and Lancaster for control of the English throne.

In 1483, King Edward IV died, leaving behind two young sons, Edward V and Richard of Shrewsbury, who were next in line for the throne. However, their uncle, Richard III, seized power and declared himself king, allegedly having the two princes imprisoned in the Tower of London and likely ordering their deaths.

This sparked a rebellion by supporters of the Lancastrian cause, who were opposed to Richard's rule. Henry Tudor, a Lancastrian claimant to the throne who had spent years in exile in France and Brittany, decided to take advantage of the situation and launched an invasion of England in 1485.

Henry's army, which included French and Breton soldiers as well as Welsh and English troops, landed in Wales and began to march eastward. Meanwhile, Richard III gathered his own forces and set out to intercept the Lancastrians.

The two armies met at Bosworth Field in Leicestershire on August 22, 1485. Richard's army was composed largely of English and Welsh soldiers, while Henry's army was a mix of Welsh, English, and foreign troops.

The battle began with a barrage of arrows, followed by a charge from Richard's cavalry. The two sides clashed in fierce hand-to-hand combat, with both sides suffering heavy losses. During the fighting, Henry's ally, the Earl of Oxford, was able to break through Richard's lines and charge directly at the king, killing several of Richard's closest companions.

Richard, seeing that his cause was lost, made a desperate charge at Henry, hoping to kill or capture him and end the battle. However, Richard's horse was killed, and he was surrounded and killed by Henry's troops. His death marked the end of the Plantagenet dynasty and the beginning of the Tudor era.

The battle lasted for around two hours, and the casualties were heavy, with estimates ranging from 1,000 to 5,000 killed or wounded. Henry emerged victorious, and he was crowned king the following day. The Battle of Bosworth is considered one of the most significant battles in English history, marking the end of the Wars of the Roses and the beginning of a new era of Tudor rule.