Question: where were the critical world war i battles fought

title: Hungary in World War I
text: On November 11 , 1918 , World War I ended for Austria - Hungary with a complete military loss , even if at the time of the collapse , all forces were standing outside the borders of 1914 . With the collapse of the army , Austria - Hungary also collapsed . The ethnic groups of Kingdom of Hungary called for independent nation - states . In the Treaty of Trianon signed on June 4 , 1920 , Hungary lost two - thirds of its territory , more than half of its population , more territory than any other country at that time ( excluding colonies ) . Eight million Hungarians left in Hungary and more than 3 million Hungarians were stranded outside of the newly established borders . New nations , such as Czechoslovakia , Poland , and Kingdom of Serbs , Croats and Slovenes were established and some already existing countries have extended their territories ( Italy and Romania ) . The southern part of Hungary was given to Yugoslavia and renamed Vojvodina . Bosnia - Herzegovina was also incorporated in Yugoslavia and Croatia became part of Yugoslavia also , after a 900 years federation with Hungary . More than 104.000 square km -- the whole of Eastern Hungary and Transylvania -- were awarded by the Entente to Romania , more than what was left for Hungary itself 93.030 sq.km . The northern part of Hungary was annexed by the newly created Czechoslovakia .