Even though he never had any formal executive position in Milorg, Kai Holst had an important role in the practical work in the organisation, and he was especially important for Milorg in the autumn of 1942 when several of the leaders were arrested by the Gestapo or had to flee to Sweden.
Trots att han aldrig hade någon formell ledarposition i Milorg, så hade Holst en viktig roll i det praktiska arbetet i organisationen, särskilt under hösten 1942, då flera av ledarna arresterades eller blev tvungna att fly till Sverige.