It seemed like a classic example of euphemistic bureaucrat-speak when, on Friday, U.S. officials referred to the deployment of Russian troops in Crimea as an "uncontested arrival" rather than an invasion.

But terminology matters here. Take the word "uncontested": The southern peninsula of Crimea, which the Soviet Union transferred to Ukraine in 1954 and which now hosts the Russian military's Black Sea Fleet, is the only region in the country where ethnic Russians are a majority (60 percent of a population of 2 million). And a good number of them favor closer relations with, if not outright annexation by, Moscow; according to one recent poll, 42 percent of Crimean residents want Ukraine to unite with Russia. That doesn't mean there are no Ukrainian nationalists or Kremlin opponents in Crimea—there certainly are—but it does mean many people in the autonomous republic, spooked by the ouster last week of Ukraine's pro-Moscow President Viktor Yanukovych, welcome Russian military intervention.

Or take the word "arrival": If this is an invasion, it's a disorienting and not yet fully formed one. There were the shadowy, Russian-speaking gunmen who fanned out across Crimea on Friday, seizing government buildings and airports. And then there was the series of seemingly orchestrated events on Saturday: Crimea's freshly minted prime minister pleading for Russian help; Russia's lower house of parliament urging Vladimir Putin to "stabilize" Crimea, the Russian president obliging; the upper house swiftly granting him the authority to use force in Ukraine. Putin is pledging to make his next move soon, as his military masses and the White House fumes. All told, we're now witnessing what Reuters is calling the "biggest confrontation between Russia and the West since the Cold War."

So what should we call the worrying developments in Ukraine? And what is Putin thinking? Back in 2008, Thomas de Waal, an expert on the South Caucasus, argued that Putin's greatest legacy is something de Waal called "soft annexation," which, at the time, was underway in Georgia's breakaway provinces of Abkhazia and South Ossetia. The idea, expressed in various forms over the years, is that Russia is pulling political, economic, and military levers—all of which fall short of traditional invasion—to exploit ethnic conflicts in countries that used to be in its orbit. And the goal is to leverage these tensions, which are often relics of the Soviet Union's messy consolidation and collapse, to gain influence in former Soviet states, while preventing these countries from moving closer to the West.