The Great War had come to an end in Europe in November 1918, but Central Europe did not come to a rest. The demise of the German, Austrian, and Russian Empires had left a geographical void, a theatre of armed conflicts between the imperial heirs for years to come: the Central European nation states. The Second Republic of Poland was one of them. Historiography has described these postwar struggles as rather unrelated conflicts. This book argues that they were much more part of one Central European Civil War. Since re-erected Poland was at the center of events, it provides a perfect case study and tells the story of this civil war in a nutshell. It challenged its neighbors on all frontiers: Ukrainians, Lithuanians, and Soviets to the northeast, Germans to the west, and Czechs to the south. A concise history of these related conflicts questions their common perception as moments of national bravado. In the embattled borderlands, nationality was not a constant, and national independence therefore not a matter of course. The people living there experienced the Central European Civil War rather as a tragedy, when brothers had to fight against brothers. Clearly defined nations did not exist in late 1918 Central Europe, they were rather forged in the fires of a civil war which shook the area for almost three years. Furthermore, in the leeway of these conflicts, Poland—like many other parts of Europe—witnessed a wave of paramilitary violence, with its own soldiers running wild beyond the battlefields.