Photos: Inside Ukraine's growing volunteer army, where the elderly and children help with war preparations

Some of Ukraine's most vulnerable populations – its elderly and children — are joining with middle-aged civilians to take up arms in preparation for a possible conflict with Russia.

According to AFP, around 100,000 Ukrainian civilians have been mobilized to bolster its active military.

Meanwhile, Russia has amassed over 150,000 troops — armed with tanks, warplanes, and artillery — outside Ukraine's borders. US officials claim the deployment is in preparation for Russian forces to "sweep down" on the capital city of Kyiv, which is home to three million people, per the Associated Press.

"The enemy is at our border," Kyiv resident Serhiy Kalinin told the BBC in February. "So everyone should be prepared."

Pensioner Dmytro Bellykov, who is in his 60s, is one of these soldiers. He returned to the recruitment center in February to join preparations to counter Russia's looming invasion, per Reuters.

"I want to make sure all my data are in order, so they don't forget about me," he told the wire agency. "I know weapons, I am not a bad marksman, I can repair weapons."

These volunteer battalions formed in 2014, when pro-Russian separatists attempted to take control of Donbas, a region in the east of Ukraine, per Spiegel.

The conflict left 13,000 people dead, many of whom were soldiers fighting in the trenches.

Over 900,000 elderly people are affected by the conflict in Ukraine's borderland cities, according to a United Nations Office for the Coordination of Humanitarian Affairs report.

A video by AP shows civilians of all ages, including children as young as four years old and teenagers, being taught by Ukrainian National Guard soldiers how to insert a magazine into a rifle.

According to Radio Free Europe, the group in the video has connections with the far-right Azov Battalion. The ultranationalist group reportedly subscribes to neo-Nazi ideology, per Al Jazeera.

The news outlet reported that pensioners such as Liudmyla Smahlenko, 65, are among the "babushkas" or grandmothers, trained by the group.

"We are already a babushka battalion. In 2014, we dug trenches, set up field bases, and since we donate our pillows and blankets, plates, mugs – we bring them everything we can," she told Al Jazeera in February.

According to AFP, volunteer soldiers train with replica Kalashnikov rifles and smoke grenades.

One of these teenagers is 15-year-old Mykhailo Anopa.

"When our father, the pastor, said there might be shelling, that Putin might attack, I started having nightmares because that's what I would think about before bed," Anopa told AFP in February.

Anopa teaches a group of some 40 boys how to dig trenches, the wire reported.

"We dug trenches to help Ukrainian soldiers. Now, we are reinforcing them. This has become our responsibility," he added.

Children in conflict zones often grow up with psychological and emotional trauma because of the violence around them, according to a report by the United Nations Children's Fund.

"We had to run home like we always have [to] when they shoot," Sergey, 16, told Foreign Policy in February. "I like to play outside, but I never know if someone will shoot me dead."