How did Henry Tudor build support against Richard III?

Henry Tudor built support against Richard III by capitalizing on the political instability and divisions within the Yorkist party following Richard’s 1483 usurpation of the throne. His strategy involved several key elements:12

• Coalition Building: Henry united disparate opponents of Richard III by promising to marry Elizabeth of York, the eldest daughter of Edward IV. This pledge bridged the gap between Lancastrian loyalists and disaffected Yorkists who were more concerned with deposing Richard than with the specific identity of his successor.12
• Exploiting Public Sentiment: Richard’s reputation suffered significantly due to rumors that he had murdered his nephews, the sons of Edward IV. This perception of him as a "wicked uncle" and tyrant alienated many members of the establishment and county elites.23
• Foreign Support: While in exile, Henry secured essential backing from France, which allowed him to recruit professional mercenaries for his invasion.12
• Strategic Alliances: Upon landing at Milford Haven in 1485, Henry gained a decisive advantage when Lord Stanley and his brother, Sir William Stanley, deserted Richard III to support the Lancastrian cause at the Battle of Bosworth Field, leading to Richard's defeat and death.142