Ukrainian People's Republic in the context of "Fourth Universal of the Ukrainian Central Council"

The Ukrainian Soviet Socialist Republic, abbreviated as the Ukrainian SSR, UkrSSR, and also known as Soviet Ukraine or just Ukraine, was one of the constituent republics of the Soviet Union from 1922 until 1991. Under the Soviet one-party model, the Ukrainian SSR was governed by the Communist Party of the Soviet Union through its republican branch, the Communist Party of Ukraine.

The first iterations of the Ukrainian SSR were established during the Russian Revolution, particularly after the Bolshevik Revolution. The outbreak of the Ukrainian–Soviet War in the former Russian Empire saw the Bolsheviks defeat the independent Ukrainian People's Republic, during the conflict against which they founded the Ukrainian People's Republic of Soviets, which was governed by the Russian Soviet Federative Socialist Republic (RSFSR), in December 1917; it was later succeeded by the Ukrainian Soviet Republic in 1918. Simultaneously with the Russian Civil War, the Ukrainian War of Independence was being fought among the different Ukrainian republics founded by Ukrainian nationalists, Ukrainian anarchists, and Ukrainian separatists – primarily against Soviet Russia and the Ukrainian SSR, with either help or opposition from neighbouring states. In 1922, it was one of four Soviet republics (with the Russian SFSR, the Byelorussian SSR, and the Transcaucasian SFSR) that signed the Treaty on the Creation of the Soviet Union. As a Soviet quasi-state, the Ukrainian SSR became a founding member of the United Nations in 1945 alongside the Byelorussian SSR, in spite of the fact that they were also legally represented by the Soviet Union in foreign affairs. Upon the dissolution of the Soviet Union in 1991, the Ukrainian SSR emerged as the present-day independent state of Ukraine, although the modified Soviet-era constitution remained in use until the adoption of the modern Ukrainian constitution in June 1996.

The Ukrainian Autocephalous Orthodox Church (UAOC; Ukrainian: Українська автокефальна православна церква (УАПЦ), romanized: Ukrayinska avtokefalna pravoslavna tserkva (UAPTs)) was one of the three major Eastern Orthodox churches in Ukraine in the late 20th and early 21st centuries, together with the Ukrainian Orthodox Church – Kyiv Patriarchate (UOC-KP) and the Ukrainian Orthodox Church – Moscow Patriarchate (UOC-MP). It began in 1921 during the dissolution of the Russian Empire as part of the Ukrainian independence movement and in order to restore the Ukrainian Orthodox Church that existed in the Polish-Lithuanian Commonwealth in 1620–1685 and was annexed by the Moscow Patriarchate without approval of the Ecumenical Patriarchate of Constantinople. The UAOC came to an end in December 2018 as it united with the UOC-KP into the newly formed Orthodox Church of Ukraine (OCU).

The UAOC, in its contemporary form, has its origins in the synod of 1921 in Kyiv, shortly after Ukraine's newly found independence. It was re-established for the third time on 22 October 1989, right before the fall of the Soviet Union. Unlike the UOC-KP, the UAOC enjoyed no recognition by the rest of the Orthodox Christian community until 11 October 2018, when the Ecumenical Patriarchate of Constantinople lifted the excommunication which had afflicted both the UAOC and the UOC-KP. It was clarified on 2 November 2018, however, that the Ecumenical Patriarchate recognized neither the UAOC nor the UOC-KP as legitimate and that their respective leaders were not recognized as primates of their churches. On 15 December 2018, at the unification council of the Eastern Orthodox churches of Ukraine, the UAOC and the UOC-KP, along with metropolitans from the UOC-MP, unified into the OCU.

The Communist Party of Ukraine (Ukrainian: Комуністична Партія України, romanized: Komunistychna Partiya Ukrayiny, КПУ, KPU; Russian: Коммунистическая партия Украины, romanized: Kommunisticheskaya partiya Ukrainy) was the founding and ruling political party of the Ukrainian SSR operated as a republican branch (union republics) of the Communist Party of the Soviet Union (CPSU).

Founded as the Communist Party (Bolsheviks) of Ukraine (CP(b)U) in 1918 in Moscow, Russian SFSR, it was the sole governing party in Ukraine during its time in Soviet Russia and the Soviet Union. While the anti-Bolshevik Ukrainian People's Republic had its own political parties of socialist ideologies, the Communist Party of Ukraine was created out of the party of Russian Bolsheviks in Ukraine known as the RSDRP(b) – Social-Democracy of Ukraine. The party was denied the right to have a separate party statute and was governed by the statute of the Russian Communist Party (Bolsheviks), All-Union Communist Party (Bolsheviks) and Communist Party of the Soviet Union. In 1952, the party was renamed as the Communist Party of Ukraine.

The Ukrainian–Soviet War (Ukrainian: українсько-радянська війна, romanized: ukrainsko-radianska viina) is the term commonly used in post-Soviet Ukraine for the events taking place between 1917 and 1921, nowadays regarded essentially as a war between the Ukrainian People's Republic and the Bolsheviks (Russian SFSR and Ukrainian SSR). The war ensued soon after the October Revolution when Lenin dispatched Antonov's expeditionary group to Ukraine and Southern Russia.

Soviet historiography viewed the Bolshevik victory as the liberation of Ukraine from occupation by the armies of Western and Central Europe (including that of Poland). Conversely, modern Ukrainian historians consider it a failed war of independence by the Ukrainian People's Republic against the Bolsheviks. The conflict was complicated by the involvement of the Revolutionary Insurgent Army of Ukraine, non-Bolshevik Russians of the White Army, and the armies of the Second Polish Republic, Austria-Hungary, and the German Empire, among others.

The Ukrainian War of Independence, also referred to as the Ukrainian–Soviet War in Ukraine, lasted from March 1917 to November 1921 and was part of the wider Russian Civil War. It saw the establishment and development of an independent Ukrainian republic, most of which was absorbed into the Ukrainian Soviet Socialist Republic between 1919 and 1920. The Ukrainian Soviet Socialist Republic was one of the constituent republics of the Soviet Union between 1922 and 1991.

The war was fought between different governmental, political and military forces. Belligerents included Ukrainian nationalists, Ukrainian anarchists, the forces of Germany and Austria-Hungary, the White Russian Volunteer Army, and Second Polish Republic forces. They struggled for control of Ukraine after the February Revolution of 1917.

The Polish–Soviet War (14 February 1919 – 18 March 1921) was fought primarily between the Second Polish Republic and the Russian Soviet Federative Socialist Republic, following World War I and the Russian Revolution.

After the collapse of the Central Powers and the Armistice of 11 November 1918, Vladimir Lenin's Soviet Russia annulled the Treaty of Brest-Litovsk and moved forces westward to reclaim the Ober Ost regions abandoned by the Germans. Lenin viewed the newly independent Poland as a critical route for spreading communist revolutions into Europe. Meanwhile, Polish leaders, including Józef Piłsudski, aimed to restore Poland's pre-1772 borders and secure the country's position in the region. Throughout 1919, Polish forces occupied much of present-day Lithuania and Belarus, emerging victorious in the Polish–Ukrainian War. However, Soviet forces regained strength after their victories in the Russian Civil War, and Symon Petliura, leader of the Ukrainian People's Republic, was forced to ally with Piłsudski in 1920 to resist the advancing Bolsheviks.

Novorossiya is a historical name, used during the era of the Russian Empire for an administrative area that would later become the southern mainland of Ukraine: the region immediately north of the Black Sea and Crimea. The name Novorossiya, which means "New Russia", entered official usage in 1764, after the Russian Empire conquered the Crimean Khanate, and annexed its territories, when Novorossiya Governorate (or Province) was founded. Official usage of the name ceased after 1917, when the entire area (minus Crimea) was annexed by the Ukrainian People's Republic, precursor of the Ukrainian SSR.

Novorossiya Governorate was formed in 1764 from military frontier regions and parts of the southern Hetmanate, in anticipation of a war with the Ottoman Empire. It was further expanded by the annexation of the Zaporozhian Sich in 1775. At various times, Novorossiya encompassed the modern Ukraine's regions of the Black Sea littoral (Prychornomoria), Zaporizhzhia, Tavria, the Azov Sea littoral (Pryazovia), the Tatar region of Crimea, the area around the Kuban River, and the Circassian lands.

The Ukrainian Ground Forces (SVZSU, Ukrainian: Сухопутні війська Збройних сил України, СВЗСУ, romanized: Sukhoputni viiska Zbroinykh syl Ukrainy), also referred to as the Ukrainian army, is a land force, and one of the eight branches of the Armed Forces of Ukraine. It was formed from Ukrainian units of the Soviet Army after Ukrainian independence, and its ancestry is traced back to the 1917–22 army of the Ukrainian People's Republic.

After the dissolution of the Soviet Union in 1991, Ukraine retained its Soviet-era army equipment. The Armed Forces were systematically downsized and underinvested in after 1991. As a result, the Ukrainian army had very little of its Soviet equipment in working order by July 2014, and most systems had become antiquated. Personnel numbers had shrunk and training, command, and support functions needed improvement. After the start of the war in Donbas in April 2014 in eastern Ukraine, Ukraine embarked on a program to enlarge and modernise its armed forces. Personnel in the Ukrainian Armed Forces overall climbed from 129,950 in March 2014 to 204,000 active personnel in May 2015, with 169,000 soldiers in the Ground Forces branch as of 2016. In 2016, 75% of the army consisted of contract servicemen. Since 2014, Ukraine's ground forces have also been equipped with increasingly modern tanks, APCs, and many other types of combat equipment.