Russian separatist forces in Ukraine in the context of "Ukrainian Armed Forces"

The Russo-Ukrainian war began in February 2014 and is ongoing. Following Ukraine's Revolution of Dignity, Russia occupied Crimea and annexed it from Ukraine. It then supported Russian paramilitaries who started a war in the eastern Donbas region against Ukraine's military. In 2018, Ukraine declared the region to be occupied by Russia. The first eight years of conflict also involved naval incidents and cyberwarfare. In February 2022, Russia launched a full-scale invasion of Ukraine and began occupying more of the country, starting the current phase of the war, the biggest conflict in Europe since World War II. The war has resulted in a refugee crisis and hundreds of thousands of deaths.

In early 2014, the Euromaidan protests led to the Revolution of Dignity and the ousting of Ukraine's pro-Russian president Viktor Yanukovych. Shortly after, pro-Russian protests began in parts of southeastern Ukraine, while unmarked Russian troops occupied Crimea. Russia soon annexed Crimea after a highly disputed referendum. In April 2014, Russian-backed militants seized towns and cities in Ukraine's eastern Donbas region and proclaimed the Donetsk People's Republic (DPR) and the Luhansk People's Republic (LPR) as independent states, starting the Donbas war. Russia covertly supported the separatists with its own troops, tanks and artillery, preventing Ukraine from fully retaking the territory. The International Criminal Court (ICC) judged that the war was both a national and international armed conflict involving Russia, and the European Court of Human Rights judged that Russia controlled the DPR and LPR from 2014 onward. In February 2015, Russia and Ukraine signed the Minsk II agreements, but they were never fully implemented in the following years. The Donbas war became a static conflict likened to trench warfare; ceasefires were repeatedly broken but the frontlines did not move.

On 24 February 2022, during the Russo-Ukrainian war, Russia launched a full-scale invasion of Ukraine, starting the current phase of the war, the largest conflict in Europe since World War II. By April 2022, the invasion's initial goal of a rapid Russian victory via decapitation had failed, with Ukraine pushing back the northern arm of the invasion and preventing the capture of Kyiv. Following this, the war transitioned to more conventional fighting in the south and east of Ukraine.

In a televised address, Russian president Vladimir Putin announced the invasion, calling it a "special military operation". He said that its purpose was to support the Russian-backed breakaway republics of Donetsk and Luhansk, whose paramilitary forces had been fighting Ukraine in the war in Donbas since 2014. Putin espoused irredentist and imperialist views challenging Ukraine's legitimacy as a state, baselessly claimed that the Ukrainian government was neo-Nazis committing genocide against the Russian minority in the Donbas, and said that Russia's goal was to "demilitarise and denazify" Ukraine.

The war in Donbas, or the Donbas war, was a phase of the Russo-Ukrainian war in the eastern Donbas region of Ukraine. The war began in April 2014, when Russian paramilitaries seized several towns. Ukraine's military launched an operation against them, but failed to fully retake the territory. Covertly, Russia's military were directly involved, and the separatists were largely under Russian control. The war continued until it was subsumed by the full-scale Russian invasion of Ukraine in 2022.

In March 2014, following Ukraine's Revolution of Dignity, Russia occupied Crimea. Anti-revolution and pro-Russian protests began in Ukraine's Donetsk and Luhansk provinces, collectively 'the Donbas'. On 12 April, a commando unit led by Russian citizen Igor 'Strelkov' Girkin seized Sloviansk and other settlements in the Donbas. Separatists declared the Donetsk and Luhansk republics (DPR and LPR) as independent states. Russia covertly supported them with troops and weaponry. It only admitted sending "military specialists", but later acknowledged the separatists as Russian combat veterans. On 15 April, Ukraine began an "Anti-Terrorist Operation" (ATO). By August 2014, Ukraine had re-taken most of its territory. Russia responded by covertly sending troops, tanks and artillery into the Donbas, helping pro-Russian forces regain much of what they had lost. DPR leader Alexander Borodai said 50,000 Russian citizens had fought for the separatists by mid 2015, excluding the regular Russian troops that invaded.

On 30 September 2022, Russia, amid an ongoing invasion of Ukraine, unilaterally declared its annexation of areas in and around four Ukrainian oblasts—Donetsk, Kherson, Luhansk, and Zaporizhzhia. Most of Luhansk Oblast and part of Donetsk Oblast had been controlled by pro-Russian separatists since 2014, while the Kherson and Zaporizhzhia Oblasts were invaded by Russia in 2022. The boundaries of the areas to be annexed and their borders were not defined; Russian officials stated that they would be defined later. None of the oblasts were fully under Russian control at the time of the declaration, nor since. If limited to the areas then under Russian control (about 90,000 km or 15% of Ukraine's territory, roughly the size of Portugal) the annexation would still be the largest in Europe since World War II.

The move occurred after internationally unrecognized referendums held days prior, which were organized by Russian occupation authorities in territories where hostilities were ongoing and much of the population had fled. It occurred seven months after the start of the invasion and less than a month after the start of the Ukrainian Kharkiv counteroffensive. The signing ceremony was held in the Grand Kremlin Palace in Moscow in the presence of occupation authority heads Leonid Pasechnik, Denis Pushilin, Yevgeny Balitsky and Vladimir Saldo, and Russian president Vladimir Putin.

The "little green men" (Russian: зелёные человечки, romanized: zelyonye chelovechki; Ukrainian: зелені чоловічки, romanized: zeleni cholovichky) were Russian soldiers who were masked and wore unmarked uniforms upon the outbreak of the Russo-Ukrainian War in 2014. They were active just before and during the Russian annexation of Crimea and carried regular weapons and equipment, but were always masked and wore distinctly unmarked green military fatigues. Russia, which had been denying any involvement in Ukraine prior to the annexation, used these little green men to give it plausible deniability on the international stage.

Between February and March 2014, these unmarked Russian soldiers occupied and blockaded the Simferopol International Airport, most of Ukraine's Crimean military bases, and the Supreme Council of Crimea. The name has also sometimes been used to refer to Russian troops during the War in Donbas; the Kremlin stated that no Russian troops were active in the region, but many little green men were operating in this region while disguised as pro-Russian separatists.

On 24 February 2022, Russia invaded Ukraine, starting the largest and deadliest war in Europe since World War II. It is a major escalation of the war between the two countries that began in 2014. The fighting has caused hundreds of thousands of military casualties and tens of thousands of Ukrainian civilian casualties. As of 2025, Russian troops occupy about 20% of Ukraine. From a population of 41 million, about 8 million Ukrainians had been internally displaced and more than 8.2 million had fled the country by April 2023, creating Europe's largest refugee crisis since World War II.

In late 2021, Russia massed troops near Ukraine's borders and issued demands to the West, including a ban on Ukraine ever joining NATO. After repeatedly denying having plans to attack Ukraine, on 24 February 2022, Russian president Vladimir Putin announced a "special military operation", saying that it was to support the Russian-backed breakaway republics of Donetsk and Luhansk, whose paramilitary forces had been fighting Ukraine in the war in Donbas since 2014. Putin espoused irredentist and imperialist views challenging Ukraine's legitimacy as a state, baselessly claimed that the Ukrainian government were neo-Nazis committing genocide against the Russian minority in the Donbas, and said that Russia's goal was to "demilitarise and denazify" Ukraine. Russian air strikes and a ground invasion were launched on a northern front from Belarus towards the capital Kyiv, a southern front from occupied Crimea, and an eastern front from the Donbas towards Kharkiv. Ukraine enacted martial law, ordered a general mobilisation, and severed diplomatic relations with Russia.