On 13 April 2014, Ukraine announced an anti-terrorist operation (ATO) to counter separatism. Its objective was to preserve the territorial integrity of Ukraine. The next day, hostilities began in the Donetsk Oblast. On 15 April, Ukrainian special forces liberated the airport in Kramatorsk occupied by separatists. Moreover, the Armed Forces of Ukraine and the National Guard of Ukraine reached the outskirts of Slovyansk and set up a blockade of the city.

On 27 April, the Luhansk People’s Republic was proclaimed, where a referendum was held on 11 May. On 24 June, the creation of the “Federal Republic of Novorossiya” was declared, which was a merger of the Donetsk People’s Republic and the Luhansk People’s Republic. The Federation was dissolved on 18 May 2015.

On 2 May 22014, an ATO helicopter was downed near Sloviansk, and on 22 May, regular military operations began. After the presidential elections in Ukraine, on 26 May, large-scale hostilities broke out, involving air and landing forces. In the battle for the airport in Donetsk, approximately 100 separatists were killed. Control over Mariupol, among others, was regained. In early July, ATO forces went on to a rapid offensive, capturing, among others, Sloviansk and Kramatorsk (5 July) and Bakhmut (6 July), Avdiivka (30 July) and Maryinka (5 August).

Fighting took place in the suburbs of Donetsk, and Luhansk was surrounded by Ukrainian troops. At the turn of July and August 2014, the separatists received support from Moscow, with military advisors, special-purpose forces and materiel. The deliveries included rocket launchers, then used by the separatists in July 2014 to shoot down several dozen Ukrainian military planes and helicopters.

Photo: Separatist barricades in Sloviansk. Photo by Aleksandr Sirota, CC BY-SA 3.0.