ENThe projections of the eastern border of the future Polish state were determined by the tradition of the pre-partition Polish-Lithuanian Commonwealth (Rzeczpospolita). In the political programmes of the 19th and early 20th centuries, the idea of regaining independence coexisted with the idea to restore the state within the pre-partition borders. The progress of nation-building processes among the peoples living in the eastern territories of the former Polish-Lithuanian Commonwealth gave rise to the need for a programme of compromise as regards the eastern border. It seemed that the federation programme, which was characteristic of socialist circles, would be such a compromise. For the political right-wing, represented by the national democrats, the ethnic factor became increasingly significant in addition to historical traditions. In the course of World War I, the conception of incorporation was adopted as the eastern territorial programme in this environment. With many differences that divided both positions, they were united by the desire to incorporate the so-called eastern borderlands within the borders of the future Polish state. Keywords: federation; incorporation; Polish political parties; eastern border; “Taken Lands”. [From the publication]