Background
As the Austro-Hungarian government collapsed, on October 18, 1918, the Ukrainian National Council (Rada), consisting of Ukrainian members of the Austrian parliament and regional Galician and Bukovynan diets as well as leaders of Ukrainian political parties, was formed. The Council announced the intention to unite the West Ukrainian lands into a single state. As the Poles were taking their own steps to take over Lviv and Eastern Galicia, Captain Dmytro Vitovsky of the Sich Riflemen led the group of young Ukrainian officers in a decisive action and during the night of October 31 - November 1, the Ukrainian militarymen took control over Lviv. The West Ukrainian People's Republic was proclaimed on November 1, 1918 with Lviv as its capital. The proclamation of the Republic, which claimed sovereignty over Eastern Galicia, including the Carpathians up to the city of Nowy Sącz in the West, as well as Volhynia, Carpathian Ruthenia and Bukovina was a complete surprise for the Poles. Although the majority of the population of the Western-Ukrainian People's Republic were Ukrainians, large parts of the claimed territory were considered Polish by the Poles. In Lviv the Ukrainian residents enthusiastically supported the proclamation, the city's significant Jewish minority accepted or remained neutral towards the Ukrainian proclamation, while the Polish inhabitants of Lviv (Polish: Lwów) were shocked to find themselves in a proclaimed Ukrainian state.

Prelude
In Lviv, the Ukrainian forces were successfully opposed by local self-defence units formed mostly of WWI veterans, students and children. After two weeks of heavy fighting within the city, an armed unit under the command of Lt. Colonel Michał Karaszewicz-Tokarzewski of the renascent Polish Army broke through the Ukrainian siege on November 21 and arrived in the city. The Ukrainians were repelled. However, the Ukrainian forces continued to control most of eastern Galicia and were a threat to Lviv itself until May of 1919. Immediately after recapturing the city, in the end of November, Poles interned a number of Ukrainian activists in detention camps.. The West Ukrainian government controlled the Drohobych oil fields with which it planned to purchase arms for the struggle, but for political and diplomatic reasons weapons and ammunition could only be sent to Ukraine through Czechoslovakia. Although the Ukrainian forces managed to push the Poles back approximately 120 km, they failed to secure a route to Czechoslovakia. This meant that they were unable to replenish their supply of arms and ammunition, and the resulting lack of supplies forced Hrekov to end his campaign.
Józef Piłsudski assumed the command of the Polish forces on June 27 and started yet another offensive. Short of ammunition and outnumbered, the Ukrainians were pushed back to the line of the river Zbrucz.

The War
In contrast to the brutality typical of the struggles occurring in former parts of the Russian empire, the Polish-Ukrainian war was conducted by disciplined and professional forces on both sides, resulting in relatively minimal civilian deaths and destruction. Approximately 10,000 Poles and 15,000 Ukrainians, mostly soldiers, died during this war The government of the West Ukrainian National Republic then disbanded, while Poland reneged on its promise of autonomy for eastern Galicia.

Aftermath

Bibliography

Battle of Lwów (1918)
Lwów Eaglets
Treaty of Riga
Komancza Republic
Romanian Occupation of Pokucie (1919)