Following this period, the Allied Powers of World War I severely pressured the Hungarians into retreating behind post-war demarcation lines as a provision to the Paris Peace Conference of 1919, their attempt to establish new nation states among the former kingdom's non-Hungarian citizens – the principal beneficiaries of which were the Kingdom of Romania, the Kingdom of Serbs, Croats, and Slovenes, the Austrian Republic, and the Czechoslovak Republic. The subsequent Treaty of Peace between the Allied and Associated Powers and Hungary was signed under protest by the latter.