The 40,000-strong threat

As many as 40,000 Russian soldiers have amassed along the border with Ukraine, according to NATO estimates. Tanks, helicopters, artillery, special forces, fighter jets and logistical units are understood to be stationed at more than 100 locations, some less than 40 kilometers (25 miles) from the border. This was the situation in mid-April as described by NATO Brigadier General Gary Deakin.

What does Russian President Vladimir Putin have in mind? Military men, politicians and analysts have been asking themselves the same question. Putin's pledge not to send troops into eastern Ukraine cannot be relied upon, wrote journalist Alexander Golz in the Moscow Times, a publication critical of the Kremlin. On the other hand, he added, since it's in the middle of being reformed it doesn't appear that the Russian army is capable of occupying large areas.

Reductions in Russian army

One of the reasons for this is that Russia has recently reduced its army, partly because of its shrinking population. According to Golz, tens of thousands of officers have been let go, and hundreds of "combat unready" troops shut down.

Before these reforms, Russia had apparently sought quantity above quality, through the mass mobilization of several million reservists. But now the government is switching over to rapid response forces. These units, Golz added, are mostly made up of the 50,000 contracted soldiers that the armed forces hire yearly. The Crimea crisis has already shown how well this works.

With this in mind, the capture and long-term occupation of larger areas - like Kharkiv, Donetsk, or Luhansk in eastern Ukraine - would present a great challenge for this army. Golz believes that at least 100,000 soldiers, or one-eighth of the total army, would be necessary to secure such regions. The occupying force would have to set up checkpoints on all major streets.

Kristian Pester of the German Institute for International and Security Affairs also sees a "danger of overextension." It takes more forces and is much more difficult to maintain long-term control over an occupied zone than it does to successfully carry out a strike, Pester told German news magazine Focus.

The Russian army is certainly capable of carrying out a quick strike: core military formations on the Ukrainian border are considered to be well-equipped with modern tanks, fighter jets, and short-range missiles.

Putin flexes his muscle

The Ukrainian army, in contrast, has 200,000 soldiers - not all of whom are loyal to the government in Kyiv - and is poorly equipped, with most of its equipment made up of Soviet leftovers that have not been renewed for years.

Eastern Europe expert Ewald Böhlke, of the Berthold Beitz Center in Berlin, explained part of the reason for this: "The Ukrainian army has been plundered by the Ukrainian oligarchy and members of the Ukrainian public services for 20 years." As a result, the army is "in a terrible state and completely demoralized," he told DW.

As such, the Ukrainian government's "anti-terrorist" campaign against pro-Russian separatists in Slovyansk has been largely unsuccessful - despite interim President Oleksandr Turchynov having activated 11,000 soldiers for it.

Putin flexed Russia's military muscle in response, with a maneuver near the border. Russian Defense Minister Sergey Shoygu announced ground troop exercises in the south and west, as well as for air units along the border. Russia had already held military maneuvers in the border region at the end of February "to prove readiness in crisis situations as well as in case of military threat."

US steps up presence

The West has also strengthened its military presence in the region. The US last week added 150 troops to a base in Polish Svidvin, and would also like to put 450 more soldiers in the Baltic nations of Estonia, Latvia, and Lithuania.

These troop deployments came about through bilateral agreements with respective governments, said US Secretary of Defense John Kirby, before adding that they do not represent a NATO decision.