In the newly independent
Second Polish Republic, the ND was initially represented by the
Popular National Union (Związek Ludowo-Narodowy), a conservative political party that advocated its program through democratic and parliamentary means. After Piłsudski's
May 1926 ''Coup d'État, the ND found itself in opposition to his
Sanacja government. The increasing control exerted by the Sanacja regime over opposition parties and its shift toward more authoritarian policies contributed to the gradual radicalization of the ND movement. In December 1926, the
Camp of Great Poland'' (Obóz Wielkiej Polski) was formed as an extra-parliamentary organization opposing the Sanacja government. The youth wing of the Camp of Great Poland gradually took control of the entire organization; by 1931, the camp became more radicalized and incorporated some militaristic elements. In 1928, the
National Party (Stronnictwo Narodowe) was founded as the successor to the Popular National Union. Initially, the new party followed the same political line as its predecessor. Following the official banning of the Camp of Great Poland, more radicalized youth joined the National Party. A generational divide between the older and younger factions of National Democrats came to a head at the 1935 party convention, where younger activists took leadership of the party. From 1936 to 1939, these personnel changes continued, and the younger generation became dominant in the party. The older generation, disagreeing with the new direction, either left active politics or exited the party. A key aspect of ND policies during this time was their focus on
Polonization of minorities. ND figures like Dmowski and
Stanisław Grabski played a role in opposing Piłsudski's proposed
Międzymorze federation and the
alliance with Ukrainian leader
Symon Petlura, contributing to tensions with Poland’s
ethnic minorities. At the same time, the ND expressed an antisemitic stance, advocating for the exclusion of Jews from certain aspects of Polish social and economic life and encouraging emigration from Poland. Throughout the 1930s, antisemitic actions and incidents, including
boycotts, demonstrations, and even attacks, were organized or inspired by National Democrats. The most prominent of these actions were carried out by a splinter group of radical young former NDs who later formed the
fascist-influenced
National Radical Camp (Obóz Narodowo-Radykalny). == World War II ==