"It was an emotional time," he says. "Often we would ask Lebanese people in the bombed south to also take their dogs off their handsâ€¦ and they would agree only on the condition that we took a child as well".
Then, as a warden of the British embassy in Beirut, he appeared to have found his vocation - finding new homes for over 300 dogs and cats left behind by fleeing British expats.
Remarkably, he along with a US animal charity managed to find the funding to charter a 747 airliner to get them to America, where they were taken in by new owners.
That act was the start of what would eventually become a voluntary organisation called Beta (Beirut for the Ethical Treatment of Animals).
But now, 10 years later, the organisation is facing its own abyss - struggling to house 500 dogs and over 150 cats.
For the past two years, traditional supporters - mainly from the US and Canada - have stopped sending money, resulting in Beta facing possible closure due to mounting debt from food suppliers.
Just recently a campaign raised over $50,000 (Â£40,000), mainly from Lebanese sponsors, but Mr Barrett does not know if Beta can carry on, as its running costs are around $10,000 per month.
He believes that the Syria war is chiefly to blame for a drop in individual funding from the US, as people prioritise sending money to groups which support Syrian refugees.
The economic cost of the influx of almost two million refugees has also indirectly fuelled a rise in the number of abandoned dogs.
Unregulated dog-selling - a fast-buck business - has led to a growth in breeding farms, and dog-fighting rings have also increased - booming ventures at a time of financial uncertainty.
"It's all business," says Mr Barrett, with a wave of his hand.
He is particularly contemptuous of irresponsible pet owners, citing cases of dogs being bought for a child but becoming a burden, with new owners even unaware of the need to toilet-train puppies or take dogs on daily walks.
The result is a gargantuan number of dogs - around 40,000, according to Beta - on the streets in this tiny country.
"Most people want pure bred dogs, it's the 'show-off' factor. A huge problem here," he says.
"Impulse buying is a real problem and the Lebanese are really affected by Paris Hilton and other celebrities as they like to copy the stars. All the people I know who have dogs tell me that they bought if from South Africa or Russia. Showing off is a big part of it."
The problem is with a section of Lebanese society - as the amount donated to Beta's recent campaign shows, many Lebanese care that animals are well-looked after.
Beta's dog pound was previously a pig farm in Beit Meri in the hills overlooking Beirut.
It looks ramshackle and, like many of its residents, abandoned and unloved.
Helena Hesayne, an architect who gives most of her time to working for Beta, is excitedly greeted by many of the dogs, whom she knows by name.
"We just rescued a dog which was being used as 'bait' for fighting dogs in Saida, who will probably have to lose his leg," she tells me. "He's too thin at the moment to operate on."
"Recently an adult man shot a dog in front of children, although often it's the case that men in Lebanon force children to do acts of cruelty against animals as a way of toughening them up," she explains.
One case, in which a video clip showed a child being goaded to push a kitten off a roof-top, was hotly debated on a local television programme.
Many of the dogs which are rescued are sent to the US, where there is a better chance of them finding new homes, Ms Hesayne says - especially dogs with three legs.
On the day we meet, she is preparing to take six on an Air France flight to a new life in the States.
As we walk through the pen she recalls several of the dogs' heartbreaking ordeals.
"This one has a leg missing, that one was tortured, this one was shot. In fact, we have a number of dogs who have bullet wounds from pistols," she adds calmly.
"The recent fund drive helped us pay about a third of our food bill which was at about $120,000," she says. "But we need more adopters and more regular sponsors. The problem is that people think we are rich just because we have 500 dogs and 150 cats, but it's not the case at all."
Martin Jay is a journalist based in Beirut reporting for a number of British newspapers and Deutsche Welle TV. Follow him @MartinRJay
While Israeli jets pounded Lebanon in the summer of 2006 in its brief war against Hezbollah, John Barrett was breaking into abandoned pet shops to rescue starving animals in cages.