At every stage of developing situation, he advanced aboveboard and reasonable policies and proposals for national reunification.

In April 1948, he convened a historic joint conference of representatives of political parties and public organizations in the north and the south of Korea, calling for unity of all the patriotic forces.

In the latter half of the 1940s and 1950s, he made public such works as "On the Building of New Korea and the National United Front" and "Against the Elections of a Reactionary Separate Government in South Korea and for the Achievement of Korea's Reunification and Independence" to stress the idea of achieving the great unity of the nation.

Especially, when the U.S. and the south Korean puppet regime were desperately working to make "two Koreas", he published the works "On the Three Principles of National Reunification", "Let Us Prevent a National Partition and Reunify the Country" and "On the Five-Point Policy for National Reunification".

In the works, he clarified the issue of achieving the national reunification in an independent and peaceful way, not dependent on armed forces or outside forces, as well as the issue of realizing the great national unity, irrespective of differences in ideology and social system, to reunify the country.

In the 1980s and 1990s, he put forth the proposal for founding the Democratic Federal Republic of Koryo and the Ten-Point Programme of the Great Unity of the Whole Nation, the embodiment of the Three Principles of National Reunification which was confirmed in the July 4 North-South Joint Statement.

From Juche 79 (1990) to 1994, he authored "Let Us Achieve the Great Unity of Our Nation", "Let the North and the South Open the Way to Peace and the Reunification of the Country in a United Effort" and other works, which gave impetus to the national reunification movement.

On July 7, 1994, a day before his death, he examined a document concerning the national reunification issue and left his signature on it.