Engineered by Lanya, the Coup of the Bureaucrats saw the Dragonlord depose Jessier the Fearful by force of arms, namely 50 Dragon warriors and 2,000 "trained functionaries," during the Fourth Cycle.
The Coup of the Bureaucrats was followed by the 200 year long "War of the Streets," which caused the new Empress to fortify the Inner Palace, afterwards the only portion that could be well defended.