With these carrots came the sticks. While North Korean generals enjoyed a significant degree of managerial autonomy, the system in which they operated remained centered around Kim Jong Il, who spied on their professional (and personal) activities and maintained control of all personnel appointments and major policy decisions. Kim protected his position at the power center, and insulated himself from any hostile takeovers by his generals behind a formidable intelligence and security apparatus.
The Military Security Command (MSC), a security agency tasked with monitoring the military, uses a variety of eavesdropping and communications interception technology to monitor the telephone conversations and Intranet usage of military commanders. The MSC also manages the bureaucratic paperwork (birth certificates, marriages, school registration, travel permits) of the spouses and children of military officers, which allows the agency and its bosses in Pyongyang to monitor the personal and family lives of military officials for signs of discontent and thwart any possible coup attempts before they reach a critical mass.
If this intricate surveillance system that he inherited from his father were to fail Kim Jong Un, he has the added protection of three of heavily armed security forces: the 3rd Army Corps, Pyongyang Defense Command, and the Guard Command. In the event of an attempted coup or power grab, the approximately 35,000-40,000 members of the 3rd Army Corps (stationed in nearby South P'yo'ngan Province) would mobilize to form a defensive ring to protect the capital. If the 3rd Army Corps became immobilized, the next layer of protection would be the Pyongyang Defense Command (PDC), a highly mobile force of 60,000 armed with tanks, armored combat vehicles, and a variety of artillery pieces that exists primarily to quell a military coup with extreme prejudice. Days before he died, Kim Jong Il conducted an inspection of the PDC, his last reported field inspection of a military unit. Joined by his son, they watched soldiers firing heavy artillery, an effective tool to deal with the military's malcontents.
The final layer around the core leadership is the Guard Command, the most technically advanced and best-trained security organization in North Korea, which I estimate to include between 70,000 to 100,000 soldiers. It runs a separate surveillance and reporting network on senior officials and is permitted to monitor all communications in North Korea, while also possessing access to surveillance reports submitted by the MSC and other internal security agencies. The Guard Command manages the critical infrastructure -- roads, tunnels, and communications -- of which Kim Jong Un would avail himself if the military threatened his authority. It also maintains and protects Kim family residential compounds and several underground fortified facilities where the leader would go in a crisis. If Kim Jong Un's actual authority evaporated, the Guard Command could mobilize chemical weapons against the leader's belligerents.
If reports about the execution of Kim Chol and other senior military officials are accurate, it was one or a combination of those three organizations that pulled the trigger. And yet, stories of the violent deaths or imprisonments of North Korean elites can be greatly exaggerated. If all the rumors of purges over the last five years were true, then the parade review platform in Pyongyang would be desolate. Nobody could be photographed attending important meetings or parliamentary sessions, nor would anyone be around to ensure that missile tests and experimental nuclear detonations ran on time. Still, amid a cytoplasm of deception, disinformation, and misunderstanding, Pyongyang palace gossip contains a nucleus of truth.