State capacity research generally focuses on improvements to a government’s ability to deliver on its policy-goals. Yet, in recent years, leaders in a number of nations have undermined high-functioning public sectors. To understand reversals of state capacity, it is necessary to examine the formal and informal dynamics at play within a nation’s bureaucracy. A formal model highlights the three trajectories a bureaucratic agency may follow in response to disruption by a political leader: temporary capture, erosion, and resistance. By prioritizing policy that is captured by special interests rather than one aligning with an agency’s legally-codified mission, leaders may undermine state capacity. Bureaucrats who care deeply about an agency’s mission can be driven to leave the public sector, thereby eroding underlying bureaucratic capacity and durably reversing high-levels of state capacity. However, agency culture may coalesce to form a norm that bolsters mission-compliance, facilitating resistance to extreme shifts and stabilizing long-term capacity.