Hal Foster and Tatyana Goryachova

Special for USA TODAY

BERDYANSK, Ukraine — The decisive campaign in Ukraine's separatist rebellion — the battle for Donetsk — is imminent, and the looming question is how much damage the jewel of the country's economy will suffer.

Fearing that the faceoff between 30,000 Ukrainian military troops and about 10,000 pro-Russian separatists will destroy much of the city of 1 million people, tens of thousands of residents have fled Donetsk.

The Ukrainian military used different strategies to recapture two other key cities in the eastern provinces of the country.

One was a small-arms attack on the separatist headquarters in Mariupol in early June, inflicting little structural damage on the port city of 480,000. The other strategy was a weeks-long artillery assault on Slovyansk in June and July that damaged about 60% of the infrastructure in the city of 110,000.

Afraid that the military will use the artillery approach, billionaire Donetsk industrialist Rinat Akhmetov went on television July 6, the day after the separatists fled Slovyansk, to plead: "Donbass (the Donetsk and Lugansk regions) must not be bombed. Cities, towns and infrastructure must not be destroyed."

President Petro Poroshenko's administration is well aware that Donetsk contributes more to the Ukrainian economy than any city in the country. It is a bastion of heavy industry that includes shipyards, coal and iron mines and steelmaking and other metals works, much of which Akhmetov owns.

The president recently pledged to use restraint in the Donetsk campaign, but the military must balance the structural damage it would inflict from air and artillery strikes against prospects for higher casualties from relying mostly on small arms.

One thing's for certain: The government wants to retake Donetsk in the worst way.

The city's capture would probably break the back of the separatist movement, although the military would still have to take Lugansk, the rebels' secondary stronghold, which has a population of 426,000.

Another reason the military is itching to fight in Donetsk is personal: to even the score with Igor Strelkov, the Russian national who has headed the separatists' combat effort.

Strelkov — a former Russian intelligence officer named Igor Girkin, according to Ukraine and the West — led the rebel campaign in Slovyansk.

He has been high-profile, appearing on Russian and separatist television networks and on Internet videos and writing a provocative daily blog about the conflict. Even the pseudonym he chose — Strelkov, meaning "shooter" — was calculated to portray him as a swashbuckler.

The defiant tone taken by Strelkov against the government in Kiev and the military has made him a hated figure in Ukraine's non-separatist world.

When government forces prevailed in Slovyansk a week ago, he and the 1,000 rebels he led retreated to Donetsk, which they vowed to hold. They began setting up defensive positions the moment they arrived.

Donetsk will be "much easier to defend than little Slovyansk," Strelkov said.

He has said in recent days that he needs about 8,000 more combatants to mount an effective defense of the city.

Kiev-based military expert Dmitry Tymchuk said he thinks the government will use the Mariupol strategy, seeking to do less damage in the Donetsk campaign.

The reserve colonel said the military used the Mariupol approach to seize Nikolaevka, a town of 18,000 near Slovyansk, on July 4, the day before the victory in Slovyansk.

Tymchuk said the military set up positions around Nikolaevka to prevent reinforcements or equipment from entering, then used small arms to take control of a building where the separatists had holed up. There were almost no civilian casualties, he said.

Although Donetsk is 50 times larger than Nikolaevka, the separatists have concentrated their forces in a handful of buildings there, Tymchuk said. That means the military could take Donetsk with a "classic anti-terrorist operation," he said.

He didn't say what would happen if the separatists fanned out across the city rather than staying in a few strongholds.

A separatist decision to disperse could lead to the worst kind of urban warfare — bloody and sustained. It would mean the military has to fight "from house to house and quarter to quarter," according to Vladimir Gorbach, a military expert at the Kiev-based Institute of Euro-Atlantic Cooperation.

Gorbach said the military will refrain from using an artillery-based strategy because of Donetsk's importance to the economy.

Tymchuk said the military took much longer than it should have to capture Slovyansk because it was reluctant for weeks to fire on fellow Ukrainians.

After more than 300 military deaths in the conflict, government troops are no longer hesitant. Their initial reluctance was rooted in the memory of more than 100 protesters killed in Kiev in February by the special forces Eagle Battalion. President Viktor Yanukovich's order for the unit to fire on demonstrators provoked such outrage that he had to flee to Russia within days.

The interim government that replaced Yanukovich disbanded the battalion because of the civilian blood it had on its hands. It has since formed three special forces units — the Azov, Dnieper and Donbass battalions.

The Azov and Dnieper units' success in capturing Mariupol means all three battalions are likely to see action in Donetsk.

Foster reported from Portland, Ore.