On 22 August 1485, Henry's army defeated Richard III's army at the Battle of Bosworth Field. When Richard III died in this battle, Henry VII became king. Other people also had a claim on the throne, and Henry did his best to stop them from taking it from him, either by executing them, putting them in prison, or trying to make friends of them, as he did with the Earl of Lincoln. Another step he took was to marry Elizabeth of York, the niece of King Richard III, who would herself have been the heir to the throne if she had not been a girl.