Four empires with vassal states in eastern europe collapsed entirely in WW1. The Freikorps were monarchist and anti-republic paramilitaries that sought to restore the German Empire. Essentially if ‘just fought and lost’ is valid, the monarchists and imperialists fought and lost the war, and the dismantling of their Empire was part of the peace treaties that ended the war. But since those treaties were also with empires that collapsed…

The ending and aftermath of World War 1 is the uncompromising context for the entire interwar period.