Dillon Hillier was working in the Alberta oil patch in Oct., 2014, when he and countless Canadians were horrified by the murders of two Canadian Forces members in St-Jean-sur-Richelieu, Que. and Parliament Hill in Ottawa. Hillier, 28, had been paying close attention to the mass atrocities by Islamic State militants in Iraq and Syria before then, but the deaths on Canadian soil had a significant impact.

“It hit home and I felt like I should go do something,” Hillier told CTV’s Your Morning on Tuesday.

Hillier quit his job, sold his car and bought a one-way ticket to Kurdistan in northern Iraq. A veteran of the Canadian Forces, Hillier had just begun adjusting to civilian life after a tour of Afghanistan when ISIS militants began gaining ground in Iraq and Syria. He said he also chose go fight overseas, to counteract the estimated 90 Canadians who had, at that time, travelled abroad to fight for ISIS.

“I felt, with my skills that I learned in my five years in the Canadian military, that I might be able to help balance the odds in a small way,” Hillier told 鶹ý Channel on Tuesday.

In his new memoir, One Soldier, Hillier recounts why he volunteered to join the Kurdish Peshmerga forces in Iraq and what it was like battling the extremist terror group for three months. He was the first-known Canadian veteran to enlist with the Kurds in their fight against ISIS.

When Hillier first arrived in Iraq in November 2014, he briefly fought alongside the Kurdistan Workers Party or PKK, a group the Canadian government has deemed a terrorist organization. During that short stint with the PKK, Hillier helped recapture a hill in the town of Tal al-Ward from Islamic State fighters which allowed local residents to return home. In the book, he admits to killing at least two ISIS soldiers that day, and states that he doesn’t regret what he did.

“I will be proud of that time of my life until the day I die.” Hillier wrote. “I think back on the ruined corpses of the jihadis and I have no remorse. In fact, I sleep easier because of it.”

Hillier told 鶹ý Channel that he just reacted in combat the way the Canadian military had trained him to. He said killing wasn’t something he wanted to do, or something that he went there explicitly to do, but he knew there was a chance it could happen.

In response to his critics, Hillier said the Kurds were protecting civilians including Sunnis, Shiites, Yazidis and Syrians, and that he wanted to help them.

“I thought it was a worthwhile struggle,” Hillier said. “I know the reason why I went there and if anybody wants to criticize me, that’s up to them.”

Hillier described ISIS as more of a country than a terrorist organization in One Soldier. He said the terrorist group controls and governs huge swathes of territory and they have the makings of a state even if they aren’t recognized internationally as one.

Hillier told CTV’s Ben Mulroney that his decision to travel to the Middle East was difficult for his parents. He said he felt bad for what he put his mother, Jane, and his father, Randy, a rural Ontario MPP, through during those three months.

“I think they came to realize that I felt I had to do this and I was over there for a good cause,” Hillier said.

The Canadian government played a role in cutting short his time with the Kurds, Hillier says. He said they pressured the Kurdish government to pull him from the frontlines out of fear for his safety and that he might be captured by ISIS.

Hillier’s memoir also discusses how painful adjusting to regular life was for him after he returned home. He recounts how he started drinking and doing drugs to cope with the violence he witnessed.

“It took me a while to come to terms with some things, but I just moved on with life I suppose,” Hillier said.

Hillier now works at an investment bank in Toronto and said he has no intention of ever returning to fight in Iraq or Syria.

One Soldier is now available online and in stores.