In 1918–1920, despite some ideological, political contradictions, the Polish politicians and scientists were forced to collaborate in the nation-state building in order to resolve the Polish territorial program at the Paris Peace Conference, taking into account historical, geographical, economic, ethnological, linguistic issues. That is why the Polish delegation consisted of scientists of mentioned fields and practitioners, who acted as the experts (41 people). The politicians occupied an important place among experts, but some of them had scientific breakthroughs. Some of them were activists of National League, nominated by the Polish National Committee (Stanisław Kozicki, Marian Seyda, Joachim Stefan Bartoszewicz, Jan Emanuel Rozwadowski), others were Józef Piłsudski’s delegates (Leon Wasilewski, Michał Sokolnicki, August Thugutt, Kazimierz Dłuski, Medard Downarowicz), and the others represented other political spectre (Franciszek Jan Pułaski – non-party, Józef Wielowieyski – the Real Politics Union, Andrzej Lubomirski – Galician Conservative of the Podolak group, Włodzimierz Tetmajer and Mikołaj Rey – folk activists). Among experts were the historians of state and law (Franciszek Bujak, Oskar Halecki, Władysław Konopczyński, Stanisław Kutrzeba, Wacław Sobieski). There were also many lawyers and economists (Władysław Grabski, Bohdan Winiarski, Józef Buzek, Roman Rybarski, Henryk Tennenbaum). At the Paris conference, the delegates (experts) were geographers, ethnologists, linguists, anthropologists (Eugeniusz Romer, Jan Czekanowski, Adam Benis, Kazimierz Nietsch, Antoni Sujkowski). The bankers and manufacturers such as Edward Natanson, Maurycy Poznański, Andrzej Wierzbicki and a navy officer Jarosław Zwierkowski played a significant role among the delegates and experts. Indeed, Polish demands were established by a small group of the Polish National Committee (Roman Dmowski, Ignacy Paderewski, Marian Seyda, Jan Rozwadowski), but delegates (experts) provided detailed data and the context for the justification