When it was founded in 1946 it emerged as the main force in the Japanese post-war labour movement and led a campaign of militant strikes.

The organization was able to mobilize a large section of white-collar workers in government and civil service sectors.

[4] The energy, coal mine and electrical equipment industry sectors were centres of strike activity.

[2] The key demands of the "October labour offensive" was establishment of minimum wage based on cost of living, improved retirement-pay system and democratization of the energy industry.

[5] In the midst of the October offensive Hosoya Matsuta (deputy general secretary of Sanbetsu) declared that the struggle of the unions was no longer merely economic but also political.

[6][7][8] He declared that the unions would topple the Yoshida cabinet through a general strike and establish a popular democratic government.

However, the organization was reluctant to become part of the corporativist system that the Economic Recovery Conference projected.

In its aftermath, the failed strike resulted in a political backlash for Sanbetsu and the Communist Party.

Restrictions on union organizing in the public sector was imposed and key communists were fired from their employments.