From biology classrooms to the battlefields of Ukraine.
Oscar Jenkins was a regular citizen when he joined the Ukrainian International Legion.
Now the Australian government has been making "urgent enquiries" with Russian authorities about a report the 32-year-old teacher from Melbourne had been killed.
A video surfaced in December showing Mr Jenkins being interrogated and hit by Russian forces.
At least seven Australians are thought to have been killed while fighting for Ukraine since Russia's full-scale invasion of the country began in February 2022.
But Mr Jenkins, who had been living in China since 2017, would be the first Australian prisoner of war killed by a foreign power since World War II.
So how did he end up fighting with the legionnaires?
Who are the international legionnaires?
The International Legion was set up by the Ukrainian government not long after the full-scale Russian invasion to recruit foreigners to help defend Ukraine.
The website states that the foreign fighters have played a key role in many crucial campaigns throughout the war and are "embedded within some of the most prominent brigades of the Armed Forces of Ukraine".
They were involved in the defence of Bakhmut, one of the bloodiest and most gruelling battles in the conflict.
The legion fighters also took part in the relentless campaign in Avdiivka.
Ukraine says its international legion is made up of about 20,000 fighters from 50 countries.
It is not known how many Australians have joined.
Glenn Kolomeitz is a former Australian soldier and lawyer who has given legal advice to members of Ukraine's foreign legion.
He has visited the troops and estimated that at any one time, about 20 to 30 Australians have been involved with the legion.
"During my time in Ukraine, I was living in legion team houses and advising and working with legion teams," he told the ABC.
"I would have seen upwards of 20 to 30 [Australians] in various units, and one in a senior staff role in Kyiv."
No military background required
The application requirements on the legion website appear very basic.
Military experience is not listed as a requirement.
Anyone between 18 and 60 years of age can apply, as long as they have no criminal record or chronic diseases.
The legion only accepts people who understand English, Spanish, Portuguese, Russian or Ukrainian.
But, speaking and understanding Ukrainian isn't a must.
"For civilians going in with no military background, I suspect there's still a vetting process, but they're not looking to see military experience," Mr Kolomeitz said.
Mr Jenkins had no previous military experience before joining the Ukraine defence forces early last year, the Associated Press reported.
Most of the Australian legionnaires Mr Kolomeitz encountered in Ukraine were highly skilled former military personnel.
They were often involved in training Western and Ukrainian civilian fighters.
"They'd be mentoring these Western legionnaires who didn't have military experience," Mr Kolomeitz said.
"I'm sure they were doing the same thing with Oscar."
What was Jenkins's role?
In the hostage video, speaking in English and broken Ukrainian, Mr Jenkins explained to his captors that he had been serving in the Donbas region to help Ukraine.
Mr Kolomeitz said he was in contact with legionnaires in Ukraine, and it appeared Mr Jenkins had been serving alongside commandos involved in major battles.
"He was popular with legionnaires and therefore he would have been popular with his Ukrainian colleagues," he said.
"You can take it that he was accepted as a fighter."
A former Australian commando in Ukraine, who has been serving since the start of the conflict, wrote in a text to Mr Kolomeitz this week: "Oscar Jenkins, the Australian that was captured, he was a friend. We served together".
Mr Kolomeitz said the commando knew Mr Jenkins was a civilian, "but once you're in the Legion, you're no longer a civilian".
"The fact that he was in a unit with this other guy, tells me that he was in the fight."
'He was in it for Ukraine'
An American legionnaire, who went by the name "Forrest", described Mr Jenkins as a selfless soldier who was highly motivated.
"He was ready to go front line, no armour, no weapon, and just there to kill Russians and keep Ukrainians safe," he told the ABC in December.
"He was in it for Ukraine."
According to a guideline for foreign volunteers published in 2024, foreign service people can earn up to 100,000 Ukrainian hryvnia ($3,820) a month.
If they're killed or physically disabled in the line of duty, they and their families can receive a one-time payment of up to 15 million Ukrainian hryvnia ($573,006), according to the same Ministry of Defence guide.
Mr Kolomeitz said he had encountered several soldiers who abandoned well-paid contracts with the Australian Army to fight in Ukraine.
"At the end of the day, it's a very altruistic approach to want to go and serve," Mr Kolomeitz said.
"I know our government doesn't like it, but to serve for Ukraine, it's not just Ukraine's fight, it's the world's fight.
"I think Oscar's motivation would have been very honourable."
What conditions do they face?
Over the years, allegations have emerged of misconduct and abuse in the legion.
The Kyiv Independent has reported extensively on allegations of illegal conduct by some commanders.
An Australian serving with the legion in Ukraine also spoke to the ABC in 2023, alleging that some incompetent Ukrainian commanders were threatening soldiers and putting them in danger.
Mr Kolomeitz had received requests for legal advice from Australians and other members of the legion.
He said the situation over the past year had "improved dramatically", especially regarding equipment and access to Western weaponry.
But in August last year, the Kyiv Independent published a follow-up to its investigations, finding that "many of the problems we shed light on back in 2022 appear to still be there".
It cited poor control over light weapons, commanders physically assaulting and threatening subordinates, and ongoing alcohol abuse in certain units.
Mr Kolomeitz said the main issue facing legionnaires was the increasing complexity of the battlefield.
The prevalence of one-way attack drones had made conditions more challenging and dangerous, he said.
And they were compromising evacuations and logistics.
"You poke your head up and there's going to be a drone there," he said.
"It's a really different battle space."
