Just how many retreating troops Ukraine will have to absorb was unclear as many servicemen in Crimea have already switched sides to Russia, but authorities say it was prepared to relocate as many as 25,000 soldiers and their families.
Humbled but defiant, Ukraine lashed out symbolically at Russia by declaring its intent to leave the Moscow-dominated Commonwealth of Independent States, a loose alliance of 11 former Soviet nations. The last nation to leave the group was Georgia, which lost a brief war with neighboring Russia in 2008 and ended up losing two separatist territories.
Vice President Joe Biden, in Lithuania trying to reassure nations bordering Russia alarmed by the sight of an expansion-minded neighbor, said the U.S. would stand by them.
"We're in this with you, together," Biden said.
Ukraine has been powerless to prevent Russian troops from taking control of Crimea, which President Vladimir Putin formally annexed Tuesday with the stroke of a pen. Crimea's absorption came after a hastily organized referendum in which the population overwhelmingly, albeit under conditions akin to martial law, voted in favor of seceding from Ukraine and joining Russia.
Russia's Constitutional Court chairman, Valery Zorkin, said Wednesday the treaty signed by Putin has been ruled valid, meaning it now only requires ratification by the Russian parliament.
On Wednesday morning, militiamen under apparent Russian command barged their way into Ukraine's naval headquarters in Sevastopol, detaining the head of Ukraine's navy and seizing the facility. The incursion, which Ukraine's Defense Ministry described as being led by a self-described local defense force, Cossacks and "aggressive women," proceeded with no resistance.
Upon gaining entrance to the base, the storming party raised a Russian flag on the headquarters square.
The unarmed militiamen waited for an hour on the square and, following the arrival of the commander of the Russian Black Sea Fleet, they took over the building.
By afternoon, they were in full control of the naval headquarters, a set of three-story white concrete buildings with blue trim.
The Ukrainian Defense Ministry said Rear Adm. Sergei Haiduk was detained and a news agency close to the Russian-backed local authorities reported that he had been summoned for questioning by prosecutors.
Later in the day, Russian Defense Minister Sergei Shoigu ordered the Crimean authorities to release Haiduk.
Andriy Parubiy, secretary of Ukraine's National Security and Defense Council, said the government was drawing up plans to evacuate its outnumbered troops from Crimea back to the mainland and will seek U.N. support to turn the peninsula into a demilitarized zone.
"We are working out a plan of action so that we can transfer not just servicemen, but first of all members of their family who are in Crimea, quickly and effectively to mainland Ukraine," Parubiy said.
Parubiy also announced Ukraine would hold military maneuvers with the United States and Britain, signatories, along with Russia, of the 1994 Budapest Memorandum. He provided no details.