The Ukrainian military delivered some welcome news to Kyiv today. Ukrainian forces have driven the separatists out of their stronghold in Slavyansk and have taken control of the city. They also appear to be on the verge of doing the same in Kramatorsk. In Slavyansk, the separatists abandoned a good deal of equipment and appear to have lost many fighters, and they lost additional assets, including armored vehicles, during the retreat.

That said, I very much doubt that Kyiv is on the verge of a decisive victory in the Donbas. The insurgents appear to have abandoned Slavyansk with most of their forces and armaments. I have seen no evidence, or claims, of large numbers of rebel fighters surrendering, and there is plenty of photographic and video evidence that the rebels have withdrawn much of their equipment, armaments, and even armor from the city, which is now showing up in Kramatorsk, Horlivka, Luhansk, and especially Donetsk. The Kyiv Post also reports that civilians are starting to leave Donetsk and Luhansk in anticipation of possible assaults on the cities by Ukrainian forces.

Anyone who followed the first and second wars in Chechnya (or for that matter the American military’s experience in Iraq) is aware of how much violence can be required for a regular military to defeat even a limited number of insurgents who take refuge in an urban area. In the Chechen case, Russian forces bombarded Grozny, a city roughly the same size as Donetsk and Luhansk, in the first war for weeks, and then suffered heavy losses after entering the city. In the second war, Russian forces essentially destroyed the city before finally taking it, again with heavy losses, this time at the hands of a few thousand insurgents.

Moreover, in neither case did the fighting end after the Russians took the city. In the first war, the Chechen rebels eventually forced the Yeltsin government to sign the so-called “Khasavyurt Agreement,” which left Chechnya, including Grozny, under their control, and in the second war it took years of intense and brutal fighting before Moscow declared the combat phase of its operations there over. And even that did not mean an end to the violence – a low-grade insurgency continues in the North Caucasus to this day. Estimates vary, but most put the total number of killed in the two wars at well over 100,000.

Of course, the Donbas is not Chechnya. The terrain is completely different, and the forested hills, high mountains, and remote villages of Chechnya facilitated the insurgency. Moreover, the Chechens are a highland people with a well-deserved reputation as fearless and ruthless fighters. But the Donbas insurgents have a huge advantage that the Chechens did not have, which is support from a major military power that borders on the conflict zone.

The Ukrainian military has managed to retake some of the key border posts it lost last month, but some are still under the control of the separatists. But even if Ukrainian forces take the remainder, they will not be able to seal the border. The Russian-Ukraine border in the current zone of conflict is some 150 miles long – and possibly longer, given that the insurgents may change tactics and zones of operation going forward. Ukrainian government sources claim that tanks and heavy weapons continue to cross from Russia into the Donbas, and I doubt that will change very much in the coming weeks.

Nor is the means by which the Ukrainian military managed to take Slavyansk and make progress against the insurgents elsewhere suggestive of a quick victory if there are battles for Donetsk and Luhansk. Ukrainian forces have been using heavy artillery, rocket attacks, and missile and bombing strikes from the air in recent weeks, which have produced significant civilian casualties and the destruction of many private homes and property. Slavyansk itself has been heavily damaged, and more than half of the city’s population has reportedly fled – it had some 120,000 residents before the current crisis, and there are estimates that only 35,000 remain there today.

Accordingly, I suspect that the optimism in Kyiv today about a possible decisive victory in the coming days or weeks will prove unfounded. Instead, Kyiv is going to face a very difficult decision about whether to try to dislodge the separatists from Donetsk and Luhansk, where using heavy artillery as in Slavyansk will produce many more civilian casualties. Kyiv should also expect Russia to increase support for the insurgents if the ATO appears to be on the verge of decisive success. And there is still a real possibility that the Kremlin will openly intervene if there is serious fighting, and many civilian deaths, in either city.