In a long-term, multi-stage research project, Peter Geiger dealt with the period of the 1930s and the Second World War. Numerous publications were produced during the course of the project. The most important are the two double volumes "Krisenzeit" (1997, 2nd edition 2000) and "Kriegszeit" (2010).
During the Second World War, the neutral, unarmed Principality of Liechtenstein lay geopolitically exposed between Switzerland and the Third Reich. The Reich regarded it as a "borderland of the German people". At the same time it was the glacis of the Sargans fortress area. The project examined the history of Liechtenstein both locally and in the frame of reference of the region, the neighbouring countries and world historical events. In the small country of Liechtenstein, which had a population of around 12,000 during the war, local, national and world history are directly interwoven, as are personal and structural history, domestic and foreign policy, micro and macro history.
The topics dealt with were: Pre-war situation, beginning of the war, military threat during the war years, neutrality, relations with the Third Reich, Switzerland and the Allies, war economy, parties, Prince, "Volksdeutsche Bewegung", danger of annexation, defence against National Socialism, German colony, foreign German NSDAP, war participants, espionage, refugees, euthanasia, end of the war, political cleansing.