Why did the relationship between AKP and NKP grow so hostile during the 1970s? How could two self-proclaimed Marxist-Leninist parties develop such tension and hate for one another and find it natural to claim that the other was a fascist party? This thesis examines the relationship between the two Norwegian parties, AKP and NKP, between 1973 and 1979 by analysing their attitude towards each other represented in material meant for both internal and external use. The thesis approaches the relation on three levels: regarding domestic issues, international issues and ideological differences. It furthermore points to the ideological differences of the parties, with NKP being a part of the Soviet-communism and AKP a part of the Maoist movement, as the underlying factor for why the relationship grew hostile during the seventies. The year 1975 stands out as a special year for the relationship as both parties consolidated ideologically, tightening its bond to respectively China and the Soviet Union. The ideological consolidation had ripple effects on how AKP and NKP perceived different issues, both at the domestic and international level. Even though AKP continued to be formally tied to the Chinese Communist Party until 1989, the party lost attraction to AKP at the end of the seventies as a result of problems within the Maoist movement, which again led to internal problems for AKP. In turn, this was one factor for why the relationship between AKP and NKP became less hostile at the end of the seventies as both parties either lacked or were reluctant to use energy on the other party after several years of hysteria between them.