Last week, masked men in camouflage garb with no insignia, dressed and equipped like Russian special forces, started taking over police stations and other government buildings in the Donets basin in Eastern Ukraine. They appeared to be working in tandem with local militias in defying the Ukrainian government.
This week, the Ukrainian government has responded by sending in military forces to counter these actions. There has been shooting and violence. But Ukraine's military doesn't seem capable of asserting control.
So Vladimir Putin's Russia, with some 40,000 troops massed just outside Ukraine, seems to have taken effective control of a significant chunk of Ukraine -- or at least denying effective control to the Ukraine government.
Whether Putin will follow up with an explicit occupation and annexation, as he did with Crimea, is unclear. Polling and previous referendum results indicate much less support for absorption into Russia in Eastern Ukraine than in Crimea.
What is clear is that Putin's actions violate the 1994 Budapest Memorandum -- signed by Russia, the U.S. and Britain -- that guaranteed Ukraine's boundaries in return for Ukraine giving up its nuclear weapons.
And what is just as clear is that the United States is unable to do anything effective to enforce its commitment.
Barack Obama's response has been tepid. Ukrainian authorities requested light arms, antitank weapons and intelligence assistance. Obama agreed to provide Meals Ready to Eat and to have them delivered by commercial trucks rather than military transport planes.
It was explained that Putin would find that provocative. But Putin surely finds provocative the Obama administration's verbal condemnations of Russia's actions and the sanctions on a handful of Russian insiders imposed by the U.S. and Europe.
Obama seems to have chosen a middle option. He has declined the recommendation of NATO military commander Gen. Philip Breedlove for strategic intelligence sharing with Ukraine. And he has declined some foreign policy experts' advice that we should acquiesce without complaint in Russia's domination of Ukraine.
Strong arguments can be made that either option would be preferable to the middle course Obama has chosen. It has left the United States, contrary to Theodore Roosevelt's advice, speaking very loudly and wielding a very small stick.
Obama came to office, as did his two predecessors, hoping to establish a cooperative post-Cold War relationship with Russia. Characteristically, and unlike Bill Clinton and George W. Bush, he blamed current problems on his predecessor and called for a "reset."
But the KGB veteran Putin, who called the demise of the Soviet Union as the greatest geopolitical tragedy of the 20th century, sees things differently. He pocketed Obama's concessions on missile defense and nuclear arms, and seeks to expand Russia's domain back toward czarist and Soviet dimensions.
Clinton and Bush encouraged the expansion of NATO and the European Union eastward to include former Soviet satellites and the Baltic nations absorbed by the Soviets in the Hitler-Stalin pact.
But the hopes that the appeal of European-style democracy would spread farther east have not been fulfilled.
Ukraine has remained an economic basket case, with a kleptocracy like Russia's but without its oil resources. Politically, it has been closely and bitterly divided between a pro-Russian east and south, and a pro-Western west and north.
The lure of the European example has been diminished by sluggish economic growth and the troubles of the euro. And if Obama has been unwilling to give military aid, European leaders dependent on Russian natural gas and investments have been wary of imposing economic sanctions.
The real danger may lie not in Ukraine but farther west. Obama's dismissal of his red line in Syria and his tepid actions on Ukraine may lead Putin to believe he will not back up other commitments.
Putin says he is protecting Russian minorities in Ukraine; what if he does so in the Baltic republics?
The British historian Christopher Clark, author of "The Sleepwalkers: How Europe Went to War in 1914," warns of "the danger, in trying to avoid conflagration in Ukraine, that Western leaders fail to provide clear signals to Putin."
The West, he says, must show "firmness and clarity in defending the real red lines established by NATO." That means more U.S. and NATO military forces in the Baltics and Poland. And beefing up U.S. and NATO militaries.
Putin's goal may be to dismantle NATO, as he believes NATO dismantled the Soviet Union, which would be the greatest geopolitical tragedy of this century.