The struggle to control eastern Ukraine has shifted in favor of Kiev as government troops take control of the eastern city of Slovyansk. Rebel fighters have left the city in what they claim is a planned retreat.

In the last couple of days, the Ukrainian military has intensified its fight against the pro-Russian forces that have created the autonomous regions of Donetsk and Luhansk. The new offensive comes after a 10-day cease-fire called by Kiev ended on June 30 because of constant fighting. According to The Associated Press, the Ukrainian army has recaptured 17 towns. Andriy Parubly, Ukraine's national security council secretary, said "Ukrainian forces now control 23 of the 36" regions in the two rebel-held provinces, according to The Globe and Mail.

However, a potential decisive blow came when Ukrainian troops took the rebel stronghold of Slovyansk. During the fighting, government troops "destroyed a tank, two combat vehicles and two armored personal carriers," according to a spokesman for Ukraine's National Security and Defense Council, as quoted by The New York Times. Once President Petro Poroshenko was informed that the city had fallen, he ordered the Ukrainian flag to be raised over the City Council building.

The New York Times reported that Ukraine Interior Minister Arsen Avakov took to social media to celebrate the retaking of the city, writing, "Run! ... The terrorists are bearing losses, surrendering."

Despite the loss, rebel forces claimed they will continue fighting. Andrei Purgin, deputy prime minister of the Donetsk People's Republic, told Interfax news agency that Ukraine attempted to raze Slovyansk, according to The New York Times.

"What would you do if you were shelled with mortars and artillery guns and pounded from the air and you had only three tanks and assault rifles?" Purgin added regarding the rebels.

The rebels said their retreat is planned and hint at retaliation. According to the Washington Post, rebel forces are trying to portray their losses as "minimal" and their retreat as part of a larger scheme.

"This time can be used effectively to complete the process of joining forces ... and increasing the supply of troops, primarily heavy weapons," said Pavel Gubarev, the "People's Governor" of the eastern Donbas region.

"Kutuzov also departed -- and in this was the plan," he said, referencing the Russian general who defeated Napoleon. "In general, Russians depart only before a decisive, victorious battle."