Following the collapse of the Russian Empire during World War I, Transcaucasia became the stage of wars between every political entity that emerged in the region (Armenia, Azerbaijan, and Georgia) and their neighbours (Ottoman Empire). The newly formed Republic of Armenia (declared on 28 May 1918) claimed most of the highlands of Karabakh, which was also claimed by the newly formed Azerbaijan Democratic Republic. Assistance from the Republic of Armenia to Karabakh was limited as it found itself fighting enemies on all fronts, but the Armenian irregulars in Zangezur and the territories formerly known as Khachen (Artsakh) managed to maintain their control over the lands, consistently fighting off offensives from Azerbaijan and quelling Muslim uprisings from within. Azerbaijan maintained control of the lowlands of Karabakh and some regions between Zangezur and Artsakh.