A Ukrainian marine speaks with his wife after a welcoming ceremony in Kyiv after their return from a military base in the Crimean port city of Feodosia.
With fears of war filling the streets above, officials in the Ukrainian capital headed underground, winding through bleak, dirty-green corridors to inspect the city's aging bomb shelters.
Kyiv Mayor Volodymyr Bondarenko said nearly all of the city's 526 shelters were in need of repairs. In the absence of budget funds, he has turned to local workers and vendors to volunteer their time and supplies. If all goes well, he said the city would be ready to provide underground shelter to all of its 2.8 million residents by October 1.
Some Ukrainians, however, may feel they can't wait that long. With Russia's continuing military buildup along Ukraine's eastern border, officials and residents alike are looking at the possibility of war with Russia as potentially days, not months, away. Moscow's pledges to avoid conflict -- most recently by Foreign Minister Sergei Lavrov, who said on March 29 Russia had "no intention" of crossing the border -- has done little to allay concerns.
"As long as foreign troops remain on our borders, the threat of conflict doesn't diminish," says Oleksandr Kuzmuk, former Ukrainian defense minister and the current head of the parliamentary subcommittee on military security and defense.
"Ukrainian troops are concentrated along the entire border with Russia; they're building up their presence and getting combat-ready. And they'll remain there until Russian troops either retreat or resort to undesirable behavior."
Nearly a quarter-century after the collapse of the U.S.S.R., Russia's militarized takeover of the Crimean peninsula is being interpreted by Ukrainians and other post-Soviets as the first step toward reclaiming its Soviet-era territory and glory.
Siege Mentality
Andriy Parubiy, the head of Ukraine's National Security and Defense Council (NSDC), has told U.S. officials that as many as 100,000 Russian troops and special forces have mobilized along the 2,000-kilometer land border with Ukraine. Unofficial self-defense units comprising so-called Russian "tourists" have also been observed inside Ukraine, in pro-Russian eastern cities like Donetsk and Kharkiv.
Yevhen Marchuk, the former NSDC secretary, said it's a situation with far more potential for danger than even the Crimean intervention.
"I don't want to paint a scenario," he said. "But you're talking about large numbers of self-organized people who won't be wearing any kind of military uniforms but will be armed with automatic weapons. This is something that can lead to dramatic combat and the deaths of many people."
Some Western analysts expressed hope of a Kremlin rethink after Russian President Vladimir Putin initiated an hour-long phone call to his U.S. counterpart Barack Obama on March 28, after weeks of hostile rhetoric between the two sides.
Ukrainian citizens, however, have already adopted a siege mentality, preparing for an invasion they believe will extend beyond eastern Ukraine to Kyiv or even further. Many Ukrainians have gone on social media to share information and advice about war preparedness.
One popular Facebook post urges residents to make personal first-aid kits, buy weapons, form neighborhood watch patrols, and stockpile gasoline, food, and batteries.
Military analysts, meanwhile, have suggested a number of possible forms a Russian invasion could take. Dmitry Tymchuk, who uses his Facebook page to publish updates from the Information Resistance news collective has posited that Russian troops may move into the Odesa and Kherson regions -- which together with Crimea form Ukraine's Black Sea coastline.
Such a move, he says would forge an economic lifeline to resource-poor Crimea. It would also create a corridor to another vulnerable piece of highly desired territory --Moldova's breakaway Transdniester, where an estimated 2,000 Russian troops are currently mobilized.
'Blitzkrieg'
Russian security expert Mark Galeotti, a professor at New York University, has suggested the first days of a Russian invasion would be marked by massive attempts to destroy Ukraine's command and communications system as well as missile and artillery attacks on key military and civilian infrastructure like roads and bridges.
"The aim would be a blitzkrieg that, before Ukraine has the chance properly to muster its forces and, perhaps more to the point, the West can meaningfully react, allows the Russians to draw a new front line and assert their own ground truth, much as happened in Crimea (though this would be much more bloody and contested)," he writes.
Others, however, have downplayed the likelihood of an invasion, saying Ukraine's surge of troop fortification along its side of the border will prove a powerful deterrent.
"Our own security forces have already been mobilizing for several weeks -- both the National Guard and army troops," says Mykola Malomuzh, a retired army general and the former head of Ukraine's Foreign Intelligence Service. "An invasion is already a considerably more complicated matter than it was before."
Even in the absence of direct aggression, some analysts suggest Moscow will use its troop presence to menace Ukraine in the run-up to the country's presidential election on May 25. That contest is widely expected to come down between pro-Western oligarch Petro Poroshenko and ex-Prime Minister Yulia Tymoshenko, who is believed by some to enjoy tacit Kremlin backing.
"Russian soldiers are going to remain at the border until the presidential election, as a way of putting pressure on Kyiv," military analyst Serhiy Zhurets says. "So it's important that the elections come off smoothly. During the race and the actual vote, Russia will create some distractions in southeastern Ukraine. That's where our National Guard and police force should be focused. In fact, they've already started doing that pretty well."
Ukraine's Defense Ministry says that it's already called out 40,000 reservists to back up existing ground troops. Nearly all are concentrated along Ukraine's eastern border, and analysts say that despite the dilapidated state of Ukraine's post-independence military, the soldiers are combat-ready and armed with vast numbers of Soviet-style tanks, rockets, helicopters, and antiaircraft missiles.
"If Putin decides to send in his troops, he has a narrow window in which to act," Russian military analyst Pavel Felgenhauer writes in "Foreign Policy," citing the need to seize on current troop readiness before Russia's spring draft brings in a wave of unseasoned conscripts. "The window of opportunity for an invasion will open during the first weeks of April and close somewhere around the middle of May."
But while troops on both sides of the divide remain on high alert, doubts continue about the ability of Ukraine's untested government to manage a home-turf war.
"Morale among the soldiers is high, for now," says Maryna Zygerlyg, an activist in Ukraine's eastern Sumy region who has helped organize provisions of clothing and food for the region's under-supplied troops.
"But what they fear more than anything is a Crimea scenario, where the leadership abandons them and local residents are powerless to help."
Yevhen Solonyna reported from Kyiv. Daisy Sindelar reported and wrote from Prague. RFE/RL Ukrainian Service correspondents, Anastasia Moskvychova and Mykola Zakalyuzhniy, contributed to this report from Kyiv. Olha Korenyeva contributed from Sumy.
