There are two examples I can think of when a monarchy was nearly turned into a democratic republic. The first example was when Simon de Montfort led England’s barons to overthrow King Henry III. This rebellion ultimately failed, but it gave rise to Parliament. The second example was during the English Civil War where King Charles I was overthrow and executed by his subjects. For a time, England was a democratic republic until King Charles II took back the crown, reestablished the monarchy, and executed all the rebels who were responsible for his father’s regicide even those who were already dead. In my third fantasy book, my main character will be spending three years undermining the authority and credibility of his regents. At the time, my character is in his minority and cannot legally rule under his own power. Despite that, he is able to weaken the power and influence of his regents. As a result, his regents decide to go to war with him by replacing the imperial monarchy with a democratic republic.