It initially struggled financially, but these slowly improved as the union was centralised.

Following years as a non-political organisation, leader Albert Raaen persuaded it to align with the social democratic movement, and it affiliated to the Norwegian Confederation of Trade Unions in 1931.

Other unions were able to take solidarity action in support of HK, which began recruiting strongly among young workers.

[1] Raaen was arrested in 1941, during the Nazi occupation, and a new leader was imposed, while the union's staff were forced to continue in their posts, although much of the union was secretly involved in the Norwegian resistance.

[1] After World War II, the union grew, with many new collective agreements and campaigned for equal pay between men and women.