The political grouping which brought together democrats was not founded in Poland until 1938. In the inter-war period, the Democratic Party (SD)’s main goal was to strengthen the parliamentary democracy system in the country, and to carry out very progressive social and economic reforms. During the Second World War – the majority of its members supported the Polish government in exile, while the rest were in favour of the Polish Workers’ Party (PPR).

It is assumed that the democrats formed their first informal groups in the Second Republic in Warsaw, and later in several other cities. They met in the so-called Democratic Clubs, until a congress of Democratic Clubs was organised in Lwów, where the SD party was founded.

Just before the outbreak of the Second World War, in April 1939, the party presented its official programme. It was very progressive for the time, especially in economic terms. It announced a planned economy, nationalisation of the main branches of industry, land reform, and full freedom of action for trade unions. The democrats acted equally expressively in the purely political sphere. As opponents of the Sanation, which ruled Poland between 1926 and 1939, they wanted to abolish dictatorship. Perceiving political trends in Western Europe and beyond the eastern borders, they expressed strong opposition to all manifestations of totalitarianism and nationalism.

The SD was mainly made up of representatives of the Polish intelligentsia and craftsmen. The group’s leading activists were Mieczysław Michałowicz (a doctor in the Polish Army, rector of Warsaw University, senator, and MP), and Mikołaj Kwaśniewski (vice-marshal of the Senate, voivode of Tarnopol, Kraków and Poznań, a doctor in the Polish Army). Both were initially supporters of the Sanation camp.

During the Second World War, the SD operated in conspiracy under the code name “Rectangle”, and its members joined the Government Delegation for Poland and the Council of National Unity. Also, many of its activists belonged to the inner loop of organisers of the Provisional Council to Aid Jews “Żegota”.

The ideological profile of the SD began to change in 1943, when the communist group decided to break away from the party, establishing the Polish Democracy Party under the leadership of Romuald Miller.

In 1945, after the Red Army entered Poland, the fate of the SD was sealed. The communist authorities made it a satellite party of the PPR and then the PZPR.