During the period after the Second World War, the party shifted its policy and started favouring more alliances with the Social Democrats.
Holmberg, together with fellow Gothenburg party cadre Knut Senander, now formed part of the leftist minority opposed to this development.
[3] At the time of the Sino-Soviet split, Holmberg became a leading figure of the small pro-Chinese wing, here the group around him in Gothenburg formed a vital part.
In some ways the grouping around Holmberg found common ground with the reformist anti-Soviet elements in the party, albeit only on a superficial level.
His group and a somewhat larger faction (in relative terms) of young party members and sympathizers launched a new organization, the Communist League Marxist-Leninists (KFML).
In the late 1950s Holmberg was hired by the Chinese authorities to translate the propaganda magazine China Pictorial into Swedish.