Russian President Vladimir Putin listens to Finnish President Sauli Niinisto prior to their talks at a residence at the Black Sea resort of Sochi, southern Russia, Friday, Aug. 15, 2014. Putin met with his Finnish counterpart to discuss interaction between the two countries, as well as international problems, first of all, the situation in Ukraine, the Kremlin press service reported. (AP Photo/RIA-Novosti, Mikhail Klimentyev, Presidential Press Service)

Now that Russia has openly attacked Ukraine, what's next?

The wait is finally over. After invading Crimea in late February, Russia has launched a full-scale invasion of Ukraine. According to NATO, over a 1,000 Russian soldiers have been deployed in Ukraine. The Russian Committee of Soldiers' Mothers puts the number at 15,000. A well-informed Ukrainian journalist estimates it at no fewer than 10,000 and possibly as high as 20,000. Naturally, Russian officials continue to deny that there are any Russian soldiers in Ukraine, but their credibility is nil and no one takes them seriously anymore.

"By seizing Mariupol, Russia would cut off the Donbas from the world."

Whatever the exact number, the Russo-Ukrainian war is now a reality.

No one knows just what Vladimir Putin has in mind, but the geography of the Russian thrusts into Ukrainian territory suggests that the Kremlin has two immediate goals. The first is to reestablish control of the territory southeast of Donetsk city, where fierce fighting has been raging for the last few weeks, and surround the Ukrainian forces stationed there. The second is to capture the port city of Mariupol (population about 492,000), which has huge metallurgical plants and serves as the Donbas's outlet to the Sea of Azov. By seizing Mariupol, Russia would cut off the Donbas from the world.

Putin's longer-term strategic goals can only be guessed at. He may be aiming to seize control of parts of southern Ukraine and thereby construct a land corridor from Russia to the illegally annexed Ukrainian province of Crimea. The peninsula's seizure has turned into an economic disaster for Russia, as Crimea is almost completely dependent on Ukraine for water, electricity, transportation, tourism, and trade. With its Ukrainian connection broken, Crimea is experiencing a deep recession marked by high inflation. A land corridor along the northern littoral of the Sea of Azov would enable Russia to rebuild some of the economic linkages Putin's ill-advised annexation sundered.

The problem with such a strategy is obvious. The Ukrainian military would resist at every step of the way. So, too, would significant portions of the local populations, either informally, or formally within the ranks of partisan movements. The result, for Russia, would be a protracted war, high casualties, and, at best, a very costly and very long occupation that could easily drain Russians' current enthusiasm for war.

Some analysts suggest that Putin is hoping to lop off a sizable chunk of southeastern Ukraine -- labeled Novorossiya, or New Russia, by him and his propagandists -- or, possibly, all of Ukraine east of the Dnipro (Dniepr) River. Either operation would entail far more costs and risks than just seizing the Azov littoral; moreover, both operations would necessitate the deployment of massive numbers of Russian troops.

"Any major military involvement in Ukraine would require deploying somewhere between 20 to 100 percent of all of Russia's armed forces, thereby leaving its vast border in Asia unprotected and undermining its ability to fight terrorism within Russia. The price Putin will have to pay will be enormous."

Two U.S. studies of the force levels necessary to deal with an insurgency, suggest the following conclusions (based on the assumption of a high degree of resistance):

In order to occupy Donetsk and Luhansk provinces alone, Russia would have to deploy 133,514 troops.

A corridor from Crimea to Donetsk would mean occupying Kherson, Zaporizhzhia, and Donetsk provinces -- which would entail 145,560 soldiers.

Occupying all seven southeastern provinces (Odessa, Mykolaiv, Kherson, Zaporizhzhia, Donetsk, Luhansk, Kharkiv) would require 317,182.

If Russia decides to conquer all of Ukraine, it would need an additional 548,587 troops--for a grand total of 865,769 troops.

Russia's armed forces currently consist of some 750,000 soldiers. Clearly, any major military involvement in Ukraine would require deploying somewhere between 20 to 100 percent of all of Russia's armed forces, thereby leaving its vast border in Asia unprotected and undermining its ability to fight terrorism within Russia. None of this need deter Putin from launching a major land war with Ukraine. But it is to say that the price he'll have to pay, in force deployments, casualties, and financial resources, will be enormous.

Short of a land corridor or a major war of aggression Putin may be aiming to seize a sizable chunk of the Donbas, perhaps the roughly one-third formerly controlled by his proxies, and turn the region into some kind of Russian protectorate or, possibly, even province à la Crimea. Such an outcome is eminently doable, as it is highly unlikely that the Ukrainian army will be able to drive out the Russians if Putin is determined to stay.

The problem with this scenario is economic. Thanks to the 100-plus days of proxy rule in the Donbas, the region has turned into a wasteland and economic sink hole. Over 2,000 people have been killed; hundreds of thousands have fled, and many are unlikely to return. Coal mines have been closed, factories have been destroyed, bridges have been blown up, infrastructure has been devastated. Industrial production in Donetsk province has fallen about 29 percent, while that of Luhansk has fallen 56 percent. Overall, the following drops have been recorded: light industry, 46 percent; chemical industry, 41 percent, machine building, 34 percent, construction materials, 22 percent, pharmaceutical production, 19 percent, metallurgy, 13 percent, and coal industry, 13 percent.

If Putin captures the Donbas, or the parts thereof that had been devastated by proxy rule, he will face an enormously expensive task of economic reconstruction and social adjustment. He may be willing to pay the price for the glory of being known as the "Donbas Liberator," but it will be a high price indeed.

"There is much evidence to suggest Putin is driven by aspirations for glory, power, and fame. If so, he could easily choose the outcome -- total war -- that could translate into World War III."

Finally, Putin may have in mind something far less ambitious: launching a counterattack and seizing bits of the Donbas in order to strengthen his hand in possible negotiations with Ukraine's President Petro Poroshenko. This would be the best-case scenario, suggesting that Putin is able and willing to act rationally in the pursuit of a politically negotiated outcome that would minimize the damage to both Ukraine and Russia. Unfortunately, there is little in Putin's recent behavior to suggest that he is capable of such calm and cool rational calculations of costs and benefits. To the contrary, there is much evidence to suggest he is driven by aspirations for glory, power, and fame. If so, he could easily choose the outcome -- total war -- that could translate into World War III.

The West -- as well as the international community -- could do much to shift Putin's calculations in the direction of rationality. The United States and Europe may be able to alert Putin to the folly of total war by imposing sanctions or other measures that would raise the economic pain felt by Russia to exceedingly high levels. An economic jolt, like an electric shock, could bring Putin back into the realm of reality.

No less important, now is the time for the West -- whether NATO, the United States, or individual European states -- to provide or sell the high-tech weaponry Ukraine needs to defend itself effectively. The argument against such a move -- that it would provoke a Russian escalation -- is no longer valid now that Russia has escalated. A well-armed Ukraine could stop Putin from embarking on any of the more alarming scenarios discussed above.

Faced with painful sanctions and a strong Ukraine, even a borderline irrational Putin might decide to search for a political solution to the awful mess he created in the Donbas.

PHOTO GALLERY Fighting in Ukraine