Ukraine's most recent gains have been around Luhansk, where troops secured positions around the city in an attempt to isolate it from outside supplies. Rebels have managed to keep supplies flowing, however, and several reports even indicate that reinforcements, including heavy armored vehicles, are arriving in the city. In fact, a train carrying armor and military trucks from Russia was seen crossing the border into Ukraine just northeast of Luhansk, suggesting that the rebels could be building a significant presence in the area. Such a force could relieve separatist forces resisting Ukrainian advances in Luhansk and could make further advances into the broader battlefield possible.
Moreover, Ukraine lost several air assets on Aug. 20-21. Ukraine confirmed the loss of an S-24 and an Su-25, both ground attack aircraft, near Luhansk. Separatists also claimed to have shot down two Mi-24 attack helicopters, but Ukraine did not confirm these losses. Ukraine's losses, incurred by separatist air defenses, are likely a result of either increased Ukrainian air operations to interdict reinforcements arriving in Luhansk or an increased presence of separatist air defenses among these reinforcements. Despite the Malaysia Airlines Flight MH17 tragedy, the activity of air defense systems such as the SA-17 Grizzly, SA-13 Gopher and SA-8 Gecko has actually increased in recent weeks, and the Ukrainian air force has taken heavy losses.
Around Donetsk, Ukrainian forces have been pushing hard from the northeast and southeast to cut the city off from its main supply line, Highway 21. Ukraine previously attempted to cut this supply line deeper into rebel territory near Snizhne and Krasnyi Luch, but elements of the 30th and 51st mechanized brigades that were spearheading the advance became disconnected from the main force and were enveloped by separatist forces. These Ukrainian forces suffered heavy losses during their advance and during their attempts to break out of the envelopment. Combined with the ability to restore control over Highway 21 and re-establish a direct supply line between Donetsk and the Russian border, this represents a significant tactical victory for the separatists.
Over the past week, Ukraine has adjusted its attempts to cut off this supply line by focusing on the area around Khartsyzk, much closer to Donetsk itself. By trying to encircle Donetsk in a much narrower pocket, Ukraine runs less of a risk of its forces becoming disconnected from the main effort and can keep its forces farther from Russian artillery. However, Ukrainian forces face more significant resistance as they operate closer to the city that still holds a large concentration of combat power. Ukrainian forces took over parts of Ilovaisk, southeast of Donetsk, but separatist forces have continued to resist them and have launched several counterattacks, some of which included armored units. If the Ukrainian forces are able to advance farther to the north to take Khartsyzk, they may be able to connect to another Ukrainian force coming in from that direction, but even then separatist attempts to break this siege would hamper Ukraine's efforts.
As the fight over the supply lines into Donetsk and Luhansk continues to develop, other separatist positions in Horlivka and Stakhanov are still resisting Ukrainian advances, and in some cases the separatists have launched counterattacks that recovered terrain. The humanitarian aid convoy that is still waiting to make its way into Ukraine from Russia could lead to an attempt to halt the Ukrainian military offensive through a cease-fire at some point. Ukraine is unlikely to agree to a cease-fire, however, since it would give the separatists an opportunity to receive significant supplies and reinforcements.
Overall, the Ukrainian offensive is still advancing, but it has met considerable resistance in critical locations, and Ukrainian forces have suffered significant losses. Separatist forces have not been able to defeat the Ukrainian offensive, but supplies and reinforcements from Russia and the separatists' ability to secure their supply lines are keeping them in the fight.
