Acta Historica Universitatis Klaipedensis

On 17 March 1938, Warsaw delivered an ultimatum to Kaunas. After the 18 years of non-existent official diplomatic relations with Poland due to the occupation of Vilnius in 1920, Lithuania was forced to renew them. The acceptance of the ultimatum in Lithuania heavily influenced the prestige of the authoritarian regime, but opened a new stage in relations between Lithuania and Poland on the eve of the Second World War. In addition to the envoy extraordinary and minister plenipotentiary to Lithuania Franciszek Charwat, Poland appointed Leon Mitkiewicz (1896–1972) as its military attaché to the diplomatic mission in Kaunas. Having scrupulously documented his life and service, Mitkiewicz observed Lithuania both before and after his appointment. He also conducted numerous political-military analyses, trying to assess the direction of international and geopolitical events. The article gives an overview of Mitkiewicz’s notes on Polish-Lithuanian relations, and Lithuania and its war potential both before and after the 1938 ultimatum.