The army recruitment office in Cherkasy, central Ukraine, has never been so busy.
More than 500 people have already turned up to enroll since Russian President Vladimir Putin declared on March 1 the right to invade Ukraine.
Katerina Shelest, a local recruiting office employee, told RFE/RL that "scores of people are showing up, including retired officers who have long been demobilized. Young men are also volunteering. We try to enroll everyone."
She added that she and her colleagues had worked virtually nonstop since Putin's announcement, "without lunch breaks, until late at night."
Ukraine has put its army on high combat alert and is calling up reservists.
In theory, all men up to 40-years old could be asked to join army ranks in the event of a full-blown war with Russia, whose military capabilities are far vaster than its neighbor's.
The army has had no trouble drumming up popular support.
As Russian forces extend their control of Crimea, Ukraine's strategic Moscow-friendly southern peninsula, volunteers have been queuing up to enlist.
Andriy Lomtev, a 21-year-old Cherkasy resident, was demobilized a year ago after serving in Crimea.
He decided to show up at the city's army recruitment office during his lunch break – hours after his own father, 46, signed up as a volunteer.
"I want to defend my people," he said. "Some of my friends have already enlisted, others are waiting to be called up. Our patriotic feelings are roused in such emergency situations."
Another fresh recruit, Cherkasy firefighter Yevhen Protsenko, says he stands ready for combat:
"I have a family and I want to protect it. It's good to see that people are not indifferent to the fate of our country, of our families," he said.
With fewer than 130,000 active military personnel -- a far cry from Russia's 845,000 -- the Ukrainian Army will need all the help it can get.
Cash-strapped Ukraine owns almost 10 times fewer tanks than Russia. It has one major warship and only about 230 combat aircraft.
Russia, which has spent billions of dollars over the past decade to upgrade and modernize its military, owns more than 30 large warships and more than 1,500 combat-capable planes.
Written by Claire Bigg in Prague based on reporting by Darya Bunyakina in Cherkasy