At the age of 50, Lee Harper thought his soldiering days were long behind him.
That was until he saw images of the Russian invasion of Ukraine unfold on his television.
Outraged by Russia's targeting of residential areas and the appalling suffering inflicted on civilians, he decided he had to do something.
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"I saw the invasion take place, children being killed, and I said to my wife 'I cannot sit back and watch this'."
He left his home in Auckland, saying goodbye to his wife, toddler and two step-children, and took a flight to Europe.
Five weeks on, he has just emerged from a stint fighting on the frontline on the outskirts of Kyiv, the Ukrainian capital.
"At times the Russians were just 20 yards away. They were fighting as hard as we were.
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"We were led to believe that the Russian artillery was not very accurate but in fact it was very accurate indeed. It was f***ing scary. I was scared every day. It's not the bullets and mortars which are frightening because you hear them. It's the missiles – you don't hear them coming in until it's too late."
He said he saw a lot of destroyed Russian armour and the devastating effects of anti-tank weapons on tank crews.
"The smell of burned human flesh will put you off bacon for life."
Harper spent 23 years in the New Zealand Defence Force, after joining up at the age of 16.
His service included stints on secondment with the British Army - 32 Heavy Regiment of the Royal Artillery - in Iraq and Afghanistan.
Savouring his first pint for weeks in a bar in Krakow in Poland, he says the rigours of combat take their toll on his 50-year-old body.
"Every single day it hurt when I put on my body armour. With the front, back and side plates, it weighs about 8kg. My knees, my hips, my shoulders – everything hurts."
He was armed with a Kalashnikov AK-74 assault weapon, a successor to the more famous AK-47, which was first in service in the Russian invasion of Afghanistan in 1979.
"We were pushed back, then we pushed forward, then we were pushed back again," he said during the interview in Krakow.
A mixed bag of nationalities are fighting for the Ukrainians, from British former Parachute Regiment soldiers to ex-French Foreign Legionnaires and former servicemen from the US, Spain and many other countries.
Harper admits his wife, 3-year-old child and 10- and 12-year-old stepchildren worry.
"They are scared, yes. A 50-year-old father shouldn't be going to war in the middle of Europe in 2022."
His motivation is deeply personal – his family on his mother's side came from Poland.
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"My grandmother was Polish, a Catholic, and she was sent to Auschwitz by the Nazis. I've come to Ukraine to protect Poland. We cannot allow Ukraine to fall under the Russian jackboot. I can't sit back and watch what happened to Poland in 1939 happen again. Where do we draw the line – Ukraine? Moldova? Enough is enough."
The automotive parts company that he works for in Auckland is keeping his job open – just as well because he intends to go back to Ukraine in the coming days.
The type of person volunteering to fight in Ukraine appears to fall broadly into three categories.
At the lower end of the scale are wannabe soldiers, "the guys who play Call of Duty too much, the Walter Mitty types who play Airsoft", as one British ex-soldier put it.
Then there are those who have served in the armed forces but did not see combat.
Thirdly, at the top end of the spectrum, there are ex-military who did experience combat.
Falling into the latter category are three British ex-servicemen encountered this week in Krakow.
The two ex-Paras and one former infantry sniper said that after crossing the border from Poland into Ukraine they were assessed as having valuable skills and picked out by the GUR, a Ukrainian military intelligence agency.
Krakow has turned into something of a staging post for foreigners heading to fight in Ukraine.
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It is connected to the rest of Europe by cheap flights and provides easy links by road and rail to the Ukrainian border to the east. Volunteers can take a train from Krakow to the western Ukrainian city of Lviv, and from there to Kyiv.
"We've had a lot of volunteers coming through in the last month," said Darius Padzan, the owner of a military supplies shop called Khaki, in the centre of Krakow.
"I've met Dutch, Norwegian, American, Canadians and lots of British. One of the British guys looked very serious. I worked with special forces soldiers for a long time and he looked like he might be ex-SAS or Marines. I know the type. He knew exactly what he needed."
The shop sells everything from backpacks and webbing to camping gear, dried food and combat jackets.
Not all the volunteers are so professional in their bearing. "Some of the Americans look like they don't have any military experience. They know something about weapons, but perhaps just from shooting on a range," said Padzan.
An American ex-soldier who has just returned from fighting on the southwest fringe of Kyiv said he and other volunteers slept in abandoned buildings.
"It's cold as f*** at night. You just have to curl up in a corner, use your rucksack as a pillow, and try to get some sleep."
Giving only his surname, Wilson, he said he had served eight years in the 2nd Infantry Brigade of the US Army and had done two tours of Afghanistan.
He, too, was relaxing in a bar in Krakow after spending three weeks on the frontline. He had just had his first shower in two weeks.
"I met a lot of British fighters, also a lot of Chechens. The Russians were shooting at us and we shot back. I saw a lot of dead bodies – they're lying everywhere on the streets. The Russians don't collect them, they don't care at all about their troops.
"I saw blackbirds pecking at the dead soldiers' faces, I guess crows or ravens."
The amount of time that volunteers spend in Ukraine varies widely – some spend a month or so fighting and then go home. "We all have kids and jobs and mortgages," as one ex-Parachute Regiment soldier from the UK put it.
He chose not to join Ukraine's International Legion because recruits, although paid, are expected to serve for the duration of the war.
The rations that he and colleagues received from the Ukrainian army were of rather mixed quality, to say the least.
"We were fed 'chicken' by the Ukrainian army but when you looked at it closely you could see it wasn't chicken – it was pigeon," said the former Para.
Other volunteers are able to stay longer in Ukraine. Harper says he plans to stick it out for several months.
Former soldiers with extensive combat experience are highly prized by the Ukrainians, said Kacper Rekawek, an expert on foreign fighters in Ukraine.
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"You have Ukrainian special forces and intelligence agencies actively fishing for the best guys crossing the border. The Ukrainian special forces all speak English so it is an easy fit. They may even have served with some of these foreigners in Afghanistan."
Ukraine's president, Volodymyr Zelenskyy, announced the formation of an International Legion in the days after the Russian invasion on February 24.
Ukrainian ministers claimed that up to 20,000 volunteers from 50 countries signed up and were on their way to fight. The true number is almost certainly far less than that.
Rekawek, from the Centre for Research on Extremism in Oslo, Norway, thinks it is in the hundreds rather than thousands.
The foreign volunteers are of more symbolic than military value to Ukraine, he said.
"It's a public relations opportunity to internationalise the crisis. Tactically, a team of guys can make a difference in a certain area, but they are not going to make a difference to the war overall.
"The Ukrainians have 300,000 personnel under arms, so the foreign volunteers are a drop in the ocean. It will ultimately be down to the locals to beat the Russians."
Should a British or American volunteer be captured, the Russians will not hesitate to turn it into a propaganda coup.
"Moscow calls them mercenaries and terrorists. It will play into their narrative of Nato aggression. They will milk it," he said.
"Of course if the Russian soldiers on the ground are very angry at the time of the capture, then I'm afraid the volunteer will meet a sorry fate there and then."
As Harper prepares to go back across the border into Ukraine, he contemplates the men he will fight.
"I don't hate the Russians. I have no animosity towards them. This is not a war against the Russians, it's a war against Putin."