The origins of Olha Bihar's call sign 'Witch' remain almost as secretive as the start date of Ukraine's long awaited counteroffensive.

"My call sign is from 2014. I'll tell the story about my call sign. But after the war," she told the ABC during a break from weapons training at a secret location in eastern Ukraine.

Olha's unit spent five months on the front lines of the Battle of Bakhmut, fighting Russian forces in one of the bloodiest battles of the 21st century.

"In Bakhmut you understand that your life and all things that you thought before were important are not important," she said. 

"You see buildings and houses blowing up and people dying, and you understand at that moment that we have something more important than money, than real estate, than cars.

"We have a very important thing: Our freedom, democracy and law."

As well as launching artillery at Russian forces, Olha has been publishing videos on TikTok about life on the front lines. 

How a young mum became a warrior:

On February 24 last year, Olha woke to the sound of Russian missiles hitting Ukraine's capital.

She went to her 18-year-old brother's room and asked him if he wanted to leave the city.

"He said, 'No, I want to defend my country'," she said.

The next day, Olha, her brother and mother joined a long queue and enlisted with Ukraine's armed forces.

Her mother and brother are now serving as combat medics.

As she prepares for the much-anticipated counteroffensive, the junior lieutenant has an extra sense of motivation.

She is fighting for a better future for her seven-year-old son.

He has spent the past 15 months living with his aunt in another country.

"One week before the invasion, I got information that Russia was ready for war," she said. 

"So I just bought the tickets, and I told my son that it's better to be in a safe place. For him, it's a little bit difficult because he likes his school, his friends, and he is asking me every time, 'Mum, when I can go back home?'

"I say to him 'a little bit later, please'. I'm happy that he never heard the sounds of explosions, and never heard the sound of sirens. It's important for his psychological health."

To explain why she made the sacrifice of being separated from her son, Olha quoted her younger brother who had just won a law scholarship to study at Kyiv University.

"My brother said, 'I don't want to study law because we don't need to study law if Russia comes to our country. There is no law in Russia and people have no rules'," she said.

"So we have to defend our country. And then we can think about the future."

Olha's family are originally from Kramatorsk in the Donbas region of eastern Ukraine.

She was there when Russian-backed separatists seized government buildings in 2014 at the beginning of the war.

For her, this is another motivation to stay and fight.

"I was a witness to Russian crimes, military crimes in 2014 when they entered our territories and took control," she said. 

"People got killed and tortured, and I cannot live with these things. I have to defend my country."

Inside the Battle of Bakhmut:

In the long days and nights on the front lines in Bakhmut, Olha said she got to know her enemy.

"In Bakhmut we've seen the real face of Russia. The face of murder. We've seen cruelties and medieval things," she said. 

Her unit, which serves inside the 241st Brigade, fought against the notorious Wagner mercenary group and other battalions from the Russian armed forces.

Wagner famously recruited murderers, rapists and drug dealers from inside the Russian prison system.

Wagner founder Yevgeny Prigozhin has estimated that 20,000 of their troops died in the city. 

Previously Wagner mercenaries have been accused of filming the execution of two of their recruits with sledgehammers after they allegedly deserted their units.

Olha described Wagner units as "the most cruel and mad" she came up against and said they forced their own troops at gunpoint to de-mine her unit's defensive positions.

"They were using people for de-mining territories. That's medieval. They were doing it to make a hole in our defence and then to attack our positions," she says.

"Behind them were guys with machine guns in case they decided to go back, their commanders would kill them."

By contrast, Olha said her unit always looks out for each other.

"Morale is very important for every unit. We are friends. Your team is your shelter. If there is bad morale, all of us could die," she said. 

Of 42 members of her unit, only three were professional soldiers prior to the invasion.

Their ranks include lawyers, an economist, a surgeon and businessmen.

"But after a year of war and three times in Bakhmut, probably all of us are professionals now," she laughed. 

"All of them have decided that the freedom is very important for them, and they can die for freedom."

While some questioned Ukraine's strategy of trying to hold Bakhmut for as long as it could, Olha is adamant it made tactical sense.

"It was the right strategy. Because if you put a finger in the mouths of Russians, they will bite off an arm," she said. 

"I think that we performed our combat task perfectly … their assault potential is now lower than before."

Dispatches from the front:

While fighting in Bakhmut, Olha became a hit on TikTok, gaining over 130,000 followers thanks to her daily dispatches from the front lines.

"That was not my idea," she said laughing.

"I have a friend, and he said, 'You know, people in Ukraine don't have the right information about Bakhmut. They think that everything is very bad. So can you make a small video?'

"Then I tried to make a video every day in Bakhmut and people started to be more confident in our success."

With her growing online following, the woman known as Witch has become one of the faces of Ukraine's resistance against Russian invaders. 

Soon, she expects to be involved in Ukraine's counteroffensive, which could begin at any moment. 

Like all units that have been rotated from out of the front lines, Olha's platoon has been busy familiarising themselves with new equipment and tactics.

"We have been studying and training so much for the counteroffensive," she said.

"We've trained every day and have had very difficult, very exhausting trainings."

Olha said her unit is confident they and the rest of Ukraine's armed forces can do the job when the time comes.

"We have the support of our allies. We have good weapons. We have high motivation. We have really good people who knows how to fight, with good battle experience," she said. 

"So I'm sure that the counteroffensive will be successful."

Original Story By | Steve Cannane & West Matteeussen