No copy of the plan has been preserved. All that is known are the basic precepts; restoring the whole plan is impossible. Work on the document was completed on February 4, 1939. The plan was based on the notions of Józef Piłsudski, who, until his death in 1935, was sure that war would arrive from the east. Thus, most army maneuvers and field fortifications were held in the east, and Poland's western border was largely neglected. Some of the fortifications can still be seen in the area around Sarny (see Sarny Fortified Area). Bunkers built by Polish Corps of Engineers in the 1930s were used in late 1940s by the Ukrainian Insurgent Army, in their guerilla skirmishes with Red Army.