The tyrant handpicked Jong Kyong-thaek, a top member of the military army of the Worker’s Party of Korea’ for the top job.
Kim is looking to reassure his power in North Korea amid fears he could face a coup by the Korean People’s Army.
North Korea’s military has long been one of the major political forces in the rogue state – boosted by Kim’s dad Kim Jong-il.
Unlike his father, Kim doesn’t trust his generals – believing they may attempt to unseat him.
Last week, Kim appointed his righthand Choe Ryong-hae to begin a purge of the top ranks of the army in a bid to secure power.
Kim’s regime has deemed the ruling military figures – called the Army Politburo – are suspected of an “irreverent attitude” towards him.
The latest backstabbing against the army has been led by Choe.
Previously, Prof Nam Sung-wook of Korea University said: "Kim seems to be using Choe to weaken the power of the military.”
North Korea’s army grew in power under Kim Jong-il who adopted a “military first” policy.
Paranoia has run through his son’s rule, beginning his reign with a series of purges and mass executions in 2011.
Kim even now appears to closing ranks as he promoted his sister Kim Yo-jong and ex-girlfriend Hyon Song-wol to top jobs.