Beyond the prize of the Black Sea peninsula, a picture is emerging of what the Russian president Vladimir Putin ultimately wants from his power play: broad autonomy for Ukraine's Russian-speaking regions and guarantees that Ukraine will never realize the Kremlin's worst nightmare - joining NATO.
The big question is whether Putin is willing to invade more areas of eastern Ukraine to achieve these goals.
For the West, it all boils down to a tough dilemma over compromising with Moscow to avert military conflict or taking a hard-line stance and risking a Russian invasion of Ukraine. Putin has sent clear signals he could take extreme measures if he doesn't get his way on keeping Ukraine out of NATO and ensuring that Ukraine remains in Russia's political and economic orbit.
Sunday's referendum in Crimea, which overwhelmingly supported joining Russia, has also raised fears that Ukraine's eastern provinces could try to hold their own independence votes.
Protesters have seized administrative buildings in several eastern cities and hoisted Russian flags over them. Some clashed with supporters of the Kiev government, raising the danger that the Kremlin could use such violence as a pretext to send in troops.
The volatile situation plays to Putin's chief stated reason for military intervention in Ukraine: protecting ethnic Russians across the former Soviet empire.
He has vowed to ''use all means'' to do that in Ukraine. And the Russian military has conducted a series of massive war games alongside the 2,000-kilometer (1,240-mile) border between the two countries in an apparent demonstration of its readiness to intervene.
''Putin is prepared to keep on pushing,'' said Fiona Hill, a Russia expert at the Brookings Institution in Washington. ''I wouldn't be at all surprised if he moves into other points into eastern Ukraine.''
While the West has ruled out a military response, some in Russia have struck a bellicose tone. A Kremlin-linked TV host ominously reminded viewers of his weekly news program Sunday that Russia is the only country that is capable of reducing the U.S. to ''radioactive ashes.''
The rhetoric by Dmitry Kiselyov, who is seen as a Kremlin mouthpiece, seemed to convey a grim warning to the United States and its allies that the Russian leader would stop at nothing to achieve his goals.
Fyodor Lukyanov, head of the Council of Foreign and Defense Policies, an association of political experts, said European Union and U.S. sanctions wouldn't stop Putin.
''If they want a (economic) war, so be it - this is the current thinking in Moscow,'' said Lukyanov.
Putin has held regular conversations with President Barack Obama and other Western leaders - and Foreign Minister Sergey Lavrov met with Secretary of State John Kerry for six hours of talks in London last week - with no visible result.
On Monday, the Russian Foreign Ministry put out a statement outlining its vision of a deal:
- Broad autonomy for Ukraine's regions that would turn the nation into a federation and would be approved by a nationwide referendum.
- The ministry suggested that Ukraine's neutral status must be guaranteed by Russia, the United States and the EU and sealed by the United Nations Security Council, with the implicit goal of preventing Ukraine's membership in NATO.
Oleksandr Chalyi, former first deputy foreign minister of Ukraine, said the underlying cause of the conflict was Russia's concern that Ukraine would join NATO. He urged the U.S. government to agree to Russia's proposal to guarantee Ukraine's neutrality.
In a conference call hosted by the Wilson Center in Washington, Chalyi offered this scenario for defusing the conflict: ''In the next days, the next hours, Russia receives a very clear message from Washington and Brussels on their proposals on the Ukrainian future: permanent neutral country with international binding guarantees.''
Hill of the Brookings Institution said that NATO wouldn't repeal its decision to keep the door open for future Ukraine membership.
''That's not going to happen,'' she said. ''I don't see that NATO would do that.''
It all means that many believe the two sides are staring at a deadlock that could potentially explode into violence.
''The Russians have now made the situation impossible with two demands: One demand is territorial change through the use of force. That is what just happened in Crimea,'' said Francois Heisbourg, an analyst at the Paris-based Foundation for Strategic Research think tank. ''The other demand is something which is actually quite unheard of in international practice since the end of the Second World War, and that is the demand by an outside power to make Ukraine into a federation.''
Lukyanov said that Russia's imminent annexation of Crimea would make it hard for the West to negotiate any compromise - but that the Kremlin apparently expects unrest in eastern Ukraine eventually to push Washington and the EU into striking a deal.
''The economy will keep deteriorating, and the political situation will grow more radical,'' he said. ''Turning it into a federation could be the only way to make the country functional.''