The former Royal Engineers staff sergeant and bomb disposal expert was diagnosed with post traumatic stress disorder, and his life went into freefall.
Paul was committed to a mental hospital, lost his wife and home, and ended up sleeping rough after starting to suffer vivid nightmares about what he had seen, including children blown up while playing with mines in Bosnia.
And at his lowest point he went into a coma and was given just two days to live during a seven-month stay in hospital caused by a stress-related illness.
But amazingly, Paul, a veteran of the Falklands, Bosnia, Kosovo, Iraq and Afghanistan conflicts during 22 years military service, pulled through and is now on the mend - and he says he owes it all to springer spaniel Irma.
Irma was the first service dog trained by military charity Bravehound, which was set up to provide companion dogs to former servicemen and women.
Paul says his new canine friend turned his life around after being matched with him just as the horrific memories of war were engulfing him.
Paul, 47, from Guildtown, Perth, says: "Before Irma came into my life I was in the lowest place, with really deep depression, anxiety attacks and suicidal thoughts.
"I came out of the army in 2012, but it is the memories of the 1994 winter tour in Bosnia which suddenly started coming back. I was taken prisoner for four days, had a pistol held to my head, and we served with the UN force near Srebrenica, where 8,500 Muslims were massacred.
"Most of the flashbacks involve children, and are so horrific I still can't talk about them today. I tried to keep it all to myself at the beginning, but now I'm having therapy.
"The flashbacks come every night, they are so vivid it is as if you are back there reliving everything, all the sounds and smells and screams. I would wake up sweating and sobbing. My body was shutting down because I couldn't cope any more.
"At my lowest point I asked for help and I got a wee cottage to live in. I was asked if I wanted a companion dog, but I could barely look after myself, I really didn't think I could handle looking after a dog as well."
Irma, now 16 months old, arrived at Paul's home last June and the charity helped him as she settled in.
But a week later he was rushed to hospital, fell into a coma for five days, and ended up staying in hospital for seven months.
Paul rcealls: "I had sepsis, my lungs were in a bad way and they had to take out my large bowel. The doctor said it was all because of stress.
"Irma slept on the bed with me during the whole time I was in hospital. She seemed to know when I was scared or in pain and would cuddle up to me. I couldn't believe it. She helped me get through it and recover my strength."
Now back at home, protective Irma never leaves Paul's side - and is helping him deal with his condition and take control of his life.
He says: "She still sleeps with me, and when I start getting the flashbacks she senses that I'm having them and wakes me up, licking my face. So I never get the full nightmares any more, because Irma's there to stop them.
"She's always with me, touching me with her head or paw to reassure me.
"Because of my post traumatic stress, noises like a dentist's drill scare me. So when I go to the dentist she lies on my chest to calm me down.
She even comes with me when I go for an MRI scan, and sits on the nurses' laps as I go into the machine.
"She's an absolutely amazing dog and I'm so glad she's been recognised for it. Thanks to her I don't get panic attacks anymore and she's put an end to my suicidal thoughts, she's changed my life that much. If everyone had an Irma in their life, the world would be a better place."