He began his Songun (military-first) leadership with an inspection tour of the Seoul Ryu Kyong Su Guards 105th Tank Division of the Korean People's Army (KPA) in August 1960.

He wisely led the KPA to remain faithful to President Kim Il Sung and the Workers' Party of Korea under the slogan "Let us defend with our very lives the Party Central Committee headed by the respected Comrade Kim Il Sung!" And he pushed ahead with the work to make the entire army a cadre army, modernize the whole army, put all the people under arms and turn the whole country into a fortress, in order to implement the WPK's military line for self-defence.

In the latter half of the 1960s, the KPA captured the U.S. spy ship "Pueblo" and shot down the U.S. spy aircraft "EC-121".

On the basis of the experience he gained in pursuing the Songun politics in the 1970s and 80s, he established the Songun political mode in an all-round way in the mid-1990s.

He took such important measures as restructuring the state mechanism on the principle of priority to military affairs and set forth the line of building the national economy with stress put on the defence industry. Then, he paid deep attention to establishing the habit of attaching importance to military affairs throughout the country.

The 1st Session of the 10th Supreme People's Assembly on Sept. 5, 1998 approved a new version of the DPRK Socialist Constitution, which suggests empowering the National Defence Commission to give a unified guidance over all works related to the nation's defence.

In his work "Let Us Thoroughly Implement the Line of Economic Construction in the Era of Songun Laid Down by the Party", published on August 28, 2003, Kim Jong Il advanced the line of giving priority to the development of the defence industry while simultaneously developing the light industry and agriculture. And he wisely and energetically led the work for implementing this line to further develop the national defence industry.

Under his guidance the country made a signal progress in the effort for putting the self-reliant defence industry on a modern and IT basis.