Ukrainian-Polish War in Galicia, 1918–19. The Ukrainian-Polish War broke out in late 1918 as a result of the Polish rejection of Ukrainian efforts to establish an independent state—the Western Ukrainian National Republic (ZUNR)—in the wake of the dissolution of the Austro-Hungarian Empire. The major issue of dispute in the conflict was control over eastern Galicia, a predominantly Ukrainian ethnic territory regarded by the Poles as an integral part of the historical Polish realm. As the boundaries of the new Polish state had not yet been established, and the ZUNR had not been granted international diplomatic recognition, the matter was ultimately reduced to a question of control by military force.
The outbreak of hostilities can be dated to 1 November, when Poles in Lviv organized resistance to Ukrainian efforts to take control of the city (see November Uprising in Lviv, 1918). Similar resistance by Poles to the Ukrainian takeover followed in Drohobych, Sambir, Jaroslaw, and Peremyshl. The Ukrainian government, in response, established the Ukrainian Galician Army (UHA) as its regular military force. Until the end of December the war remained a series of local skirmishes that developed into a standoff in which the Poles controlled Lviv and certain territories east of the city. The command of the UHA did not possess an overall operational plan, and the Poles simply tried to maintain their position. By January 1919 the front stretched from Baligrod (Balyhorod), in the Carpathian Mountains, along the Khyriv–Peremyshl railway line (with the Poles in possession of Peremyshl) to Lviv (in Polish hands) and then looped around in a clockwise direction to the Uhniv–Rava-Ruska area, from which it went northward.
When the Polish government in Warsaw began to dispatch regular troops to eastern Galicia, the conflict assumed a new dimension. By January 1919, Polish numbers reached about 20,000 men. On 15 February the UHA (some 40,000 men) began a great offensive (the so-called Vovchukhy Operation) toward Lviv, the Peremyshl–Lviv railway line, Rava-Ruska, and Belz. By the end of the month a short armistice was being enforced by the Entente (as a result of negotiations by the Berthelemy Mission). On 2 March, however, the UHA renewed the attack and was able to encircle Lviv. On 19 March the Polish divisions broke through the Ukrainian lines in the region of Horodok (Lviv region) and retook the Lviv–Peremyshl corridor.
On 2 April the Supreme Council of the Paris Peace Conference established a commission headed by Gen Louis Botha to arrange an armistice between Poland and Ukraine. The proposed demarcation line it suggested (Lviv to be on the Polish side, Drohobych and Boryslav, on the Ukrainian side) was accepted by the government of the ZUNR but rejected by the Polish government, which claimed the right to take over the whole of eastern Galicia.
By that time the Poles had acquired the means to enforce their will. On 17 March the Supreme Council of the Paris Peace Conference had given permission for the army of Gen Jozef Haller (six divisions, with about 68,000 men) to be transferred from France to Poland for the express purpose of securing a frontier against potential Bolshevik attack. It was moved in April. Although the Polish prime minister, Ignacy Paderewski, had assured the council that the army would not be sent to eastern Galicia, the troops were nonetheless being deployed there by mid-May. On 14 May a Polish force of approx 50,000 men attacked from the regions of Peremyshl, Horodok (Lviv region), and Lviv; in six days it had occupied Turka, Drohobych, and Stryi in the south and Kaminka-Strumylova in the north (the Polish offensive also included Volhynia). By 27 May the Poles had taken Halych and Stanyslaviv and were making contact with the Rumanian troops which entered Pokutia. The protests of the Entente and the need to transfer the armed forces to the west (because of fears of a German attack against Poland) stopped the Polish offensive on the Brody–Zolota Lypa River line.
On 7 June the reorganized UHA (with Gen Oleksander Hrekov as commander in chief from 9 June) embarked upon the Chortkiv offensive, which in two weeks reached the Brody–Krasne–Peremyshliany–Hnyla Lypa River line. The UHA troops were now about 40 km from Lviv, but they began to run short of ammunition and provisions. At the same time the international situation of the ZUNR also changed for the worse: following the defeat of the Army of the Ukrainian National Republic in Volhynia by the Red Army the Supreme Council of the Paris Peace Conference empowered Poland (25 June) to take over the whole of eastern Galicia up to the Zbruch River in a move intended to block a potential Bolshevik onslaught to the west. The council, however, did not regard that resolution as a final decision on the political future of eastern Galicia.
After new Polish troops (under the command of Jozef Pilsudski) were transferred to the east, they commenced a decisive offensive on 28 June. On 5 July the Poles reached the line of the Strypa River, and on 15 July they seized Ternopil and the area on both sides of the Seret River. Despite the defeat the UHA forces (about 80,000 men, including 36,000 in the first line of the front) retained their combat readiness and on 16–18 July crossed to the eastern side of the Zbruch River, where the UNR Army was stationed. The government of the ZUNR also crossed the Zbruch River to Kamianets-Podilskyi.