Stopping Putin: The Military Option

President Barack Obama is getting anxious that Russian president Vladimir Putin is on the point of invading Ukraine.

"You've seen a range of troops massing along [the Russian/Ukraine] border under the guise of military exercises," he told CBS News last night. "But these are not what Russia would normally be doing. And, you know, it may simply be an effort to intimidate Ukraine. Or it may be that they've got additional plans."

So far, the West has deployed its economic and diplomatic might to punish and deter Russian President Vladimir Putin from those "additional plans" -- invading the rest of Ukraine.

Yet the West's strongest option remains untouched: Military action.

While Russia rolled its forces into Crimea, the West clearly has kept its armies confined to barracks. So far the U.S. and its NATO allies have merely offered Ukraine limited military support and have flexed their military muscles in other ways.

Earlier this month, as the crisis in Ukraine escalated, the U.S. announced training exercises in Poland for F16 fighter planes and C130 transport planes. And generals in NATO headquarters in Brussels are planning for what could come next.

An estimated 30,000 Russian troops are currently positioned near Ukraine's eastern border. Russia's defense minister assured his American counterpart last week that the Russian Army will not move further into Ukraine. But Ukrainians – and many observers elsewhere – fear a Russian invasion is possible.

"The force that is at the Ukrainian border now to the east is very, very sizable and very, very ready," said General Philip Breedlove, NATO's Supreme Allied Commander.

A Russian push further into Ukraine could leave the U.S. and NATO in a tight spot: Kiev is a NATO partner, but is not party to the mutual defense pact set up in 1949 in response to the Soviet threat to expand into the western Europe.

A Ukraine-Russia fight would be a rout. Russia's army is the world's second strongest, with over 700,000 active duty troops compared to Ukraine's 160,950. The Ukrainians have around 400 military aircraft, while Russia has over 3,000.

On its own, Ukraine wouldn't stand a chance. With NATO's help, however, the fight would look very different.

NATO countries collectively spend between somewhere between $850 and $900 billion a year on defense, dwarfing Russia's $76.6 billion annual budget. The alliance has access to around 70,000 U.S. troops in Europe alone, not to mention the armies of the other 27 members. NATO also has a 13,000-strong rapid response force composed of land, air, maritime and special forces that can be deployed immediately.

If NATO wanted to wade into a battle with Russia, Moscow would meet a formidable foe. NATO could deploy its rapid response force to halt the Russian advance or provide air support to the beleaguered Ukrainian military.

But military strategists reject those options as profoundly unlikely.

No matter what Russia does in Ukraine – even in the case of a full-scale invasion – there is little chance NATO, or the U.S. acting independent of the alliance, will engage in a shooting war with Russian troops.

War with Russia would escalate the Crimea crisis to an extent that no one in Washington, or likely even in the much more bellicose Moscow, would want. Russia and the United States have the world's two largest stockpiles of nuclear weapons – a war could soon get ugly.

"There are going to be moments where military action is appropriate," President Barack Obama said in Brussels on Tuesday. "There are going to be some times where that's not in the interests – national security interests of the United States or some of our partners."

A Russian invasion of Ukraine would not, apparently, be one of those moments.

The U.S. military can still play a role in the Ukraine crisis, though, in the form of aid to Ukraine and threatening moves in other countries on Russia's borders.

"I'd guess there's a great deal of planning underway for things like sharing information, sharing intelligence, providing logistical support, providing lethal and non-lethal assistance, providing trainers and advisers," says James Stavridis, who was the Supreme Allied Commander of Europe from 2009 to 2013 and is now the dean of the Fletcher School of Law and Diplomacy.

Some military assistance has already started moving from U.S. forces to their Ukrainian counterparts. The focus for now, the Pentagon says, is on non-lethal aid, like rations.

Ukrainian officials are hoping for something a little stronger than medical supplies and freeze-dried meals. When Ukraine's prime minister, Arseniy Yatsenyuk, visited President Obama in the White House on March 12, he requested arms. He was offered 25,000 cases of "meals ready to eat" for his armed forces, but his plea for weapons and ammunitions remains pending.

Some Republican members of Congress have demanded the U.S. go further, saying Washington should provide Kiev with all the military equipment it has asked for. "You can do non-combatant military aid in a way that allows [Ukraine] to defend themselves," said Mike Rogers, a Republican from Michigan who heads the House Intelligence Committee.

But even Rogers says he doesn't want to see American "boots on the ground" in Ukraine.

Why is no one willing to commit the use of forces to defend Ukraine in the case of an invasion? Beyond fear of confrontation, the answer lies in NATO's design.

Ukraine is not a member of NATO, whose 28 members have a mutual defense agreement. And while Brussels and Washington view Ukraine as an ally, strategic interests in the former Soviet state are not vital.

"If Russia were to invade Germany, that would be a vital interest," says John R. Deni, a research professor of security studies at the U.S. Army War College. "But we have to be bracingly realistic in our assessment of what our interests are."

In 2004 Bulgaria, Romania, Slovakia, Slovenia and the three Baltic states joined NATO. Bringing in members from the former Soviet Union expanded the alliance's power but also brought with it new issues.

"When NATO expanded to include these countries, there was a recognition that that meant they were coming into an alliance that would guarantee their security. But I don't know if anyone came to grips with the notion that they might have to do something about that someday," says James Goldgeier, the dean of American University's School of International Service and a scholar of NATO.

At the time, NATO decided to keep the new members relatively uninvolved militarily in the alliance, not moving major defense infrastructure into the Baltics or Southeastern Europe in an effort to maintain good relations with the post-Soviet Kremlin. Similarly, attempts by Ukraine and Georgia in the mid-2000s to join the treaty were held up in order to not antagonize Moscow.

In 2009, plans were scrapped for NATO to install missile launching sites in Romania and Poland alongside an independent Polish missile defense system. Though the anti-missile system was to protect Europe from potential Iranian threats, the decision not to implement it was done to prevent the souring of relations with the Kremlin.

This week, however, NATO agreed to go ahead with building 10 missile silos in Poland that will be coordinated with a U.S. tracking radar base in the Czech Republic. While the British Defense Minister Philip Hammond stressed the "missile defense program is not aimed at Russia" but at "rogue states" such as Iran, U.S. defense secretary Chuck Hagel said the new deployments would "benefit Poland, the United States and the entire trans-Atlantic alliance.".

But NATO's caution doesn't seem to have discouraged Russia from its adventurous foreign policy. As Putin now reasserts Russia's interests in its neighbors, NATO may have to think a lot more about how to protect its smaller member states – and assure them that the treaty's Article 5, which guarantees mutual defense, actually means something.

Gen. Philip Breedlove, the current Supreme Allied Commander of NATO, said Tuesday that the alliance takes threats to the Baltics particularly seriously. "We need to think about our allies, the positioning of our forces in the alliance and the readiness of those forces…such that we can be there to defend against it if required, especially in the Baltics and other places," he said.

Germany's defense minister also said recently that "it's important to make clear that NATO isn't just something on paper" and called for NATO troops to be stationed in the Baltics.

In addition to sending planes to Poland, the alliance could send a strong message to Russia by increasing the length of troop rotations in the Baltic countries and Romania and Bulgaria.

Statements and symbolic actions like these might be enough to help reassure Baltic leaders and send a message to Putin that even if the West allows Ukraine to come under the Kremlin's control, NATO members are strictly off limits.

Adm. Stavridis says it's unlikely Russia will violate the territorial integrity of a NATO member, even Estonia, which has a significant ethnic Russian population. NATO countries collectively "spend $850 to $900 billion a year on defense," Stavridis says. "Compare that to the capabilities of Russia. I think it's very unlikely Russia would push into a NATO country."

But that doesn't mean generals and admirals aren't preparing themselves for the worst.

"I would assume that within the halls of [NATO's military headquarters] they are giving a great deal of thought to what the options are out there," says Deni, who previously advised U.S. military commanders in Europe. "That's just prudent military planning."