The creation of the USSR and the foundation of the International promoted the foundation of many communist parties to spread the revolution! in 1921 the Portuguese Communist Party was founded and it started seeding the need for revolution.
Post-WWI Portugal was under a severe political crisis with the government changing hands constantly until in 1926 a military coup overthrew the government and installed a military government until one man, Antonio Oliveira Salazar, in 1932 was pointed head of state and created Estado Novo a fascist authoritarian dictatorship!
During 41 years it oppressed its own people, the communist party which was clandestine, helped to organize the workers to get better pays.
In 1974 there was another military coup that was meant to liberate Portugal and establish democracy legalizing the Communist Party. Nowadays its the oldest active party, its the only one to defend the interests of the workers siding with the biggest workers union in Portugal