It was late last month when a savvy young Canadian diplomat saw and heard the warning signs in southwestern Syria.

The withdrawal of U.S. protection for rebel-held areas and the onslaught of forces loyal to Syrian leader Bashar al-Assad meant only one thing for hundreds of White Helmet volunteers and their families.

They were living on borrowed time.

It wasn't long before "extremely forceful" notices were landing in the inboxes of Foreign Affairs Minister Chrystia Freeland and her top officials, multiple, confidential government and diplomatic sources told CBC News.

The information arrived on the eve of the NATO leaders' summit in Brussels earlier this month.

While the world remained transfixed by the meltdown in relations between the Trump administration and the U.S.'s closest allies, a major, dramatic rescue mission — bringing the White Helmets out of Syria and into Jordan — began to take shape.

Freeland raised the plight of the White Helmets in the region of Daraa — the cradle of the rebellion against Assad — in an emotional, off-the-cuff address during a formal dinner with her NATO counterparts.

According to federal sources, she said they had a "moral obligation" to help people that Western nations had publicly lauded.

Sources in the diplomatic community corroborated the account.

The White Helmets are courageous volunteers and first responders who risk their lives to help their fellow Syrians. Our thanks to Israel, Jordan, US, UK, Germany and our other partners who have worked closely with Canada to make the evacuation of WH possible. —@cafreeland

Both Freeland and Prime Minister Justin Trudeau went further and used what are known as "formal interventions to draw attention to this" at the summit, said federal government sources, who could not speak publicly because of the sensitivity of the file.

The fact decision-makers were at the same table made all the difference to the international rescue plan at that critical moment.

"It would have been far more difficult had we not had that meeting, which coincided so closely with events on the ground," said one senior official.

"There was a real chance for everyone at the highest level to very quickly come to a consensus to do something."

Once back in Canada, the sources say, Trudeau ordered a marshalling of federal departments, including Foreign Affairs, Immigration and Public Safety, all of which were required to create the conditions for rescue and resettlement.

Netanyahu says U.S., Canada asked for help

Getting the White Helmets out of that portion of Syria with both the Israeli and Jordanian borders closed was among the biggest obstacles.

Israeli Prime Minister Benjamin Netanyahu revealed Sunday that both the U.S. and Canada asked for his country's help in guaranteeing safe passage to Jordan for the volunteers.

In order to broker the arrangement, the sources said, former Liberal justice minister and human rights lawyer Irwin Cotler was enlisted.

Therefore, I approved their passage through Israel to additional countries, as an important humanitarian gesture.<br><br>Concurrently, we will not stop taking action in Syria against Iran's attempts to establish a military presence there. —@netanyahu

Convincing the volunteers to leave their homes, and deciding who among families would depart and assemble them in a country where there is spotty communication were also enormous hurdles.

Sources said the initial plan called for three large groups, totalling up to 1,300 people, to move separately towards the border.

Only one group made it all the way to a United Nations camp, where Canada, Germany and Britain had to guarantee quick processing and resettlement.

The move, dramatic enough because it happened under the cover of darkness on Saturday, was made even more precarious with the presence of two pregnant women, one of whom went into labour and delivered during the move.The hundreds of volunteers and their relatives who didn't leave are reportedly on the move to other parts of the country still under rebel control.

Many White Helmets won't take help, expert says

They are still in danger, but it is unclear how willing they will be to leave.

"As the regime retakes territory, it will frankly be seeking retribution, and many of these people will be tortured if not killed," Bessma Momani, an author and Middle Eastern expert at the University of Waterloo in Ontario, said in an interview with CBC News.

"I think a lot of the White Helmets will stay until the end. They have sacrificed too much, knowing that it is them — and them only — that will be there to rescue the civilians who are invariably going to be trapped unsafe and at the hands of a very cruel regime as it moves forward in taking territory back. And I think that's why they are so commendable, but also tragically they will be the last ones I think to take the offer of help."

Syria Civil Defence group, better known as the White Helmets, scour through rubble after bombings to find survivors 0:44

The notion the White Helmets would be targeted for retribution was underlined for Canadians by the volunteers themselves in recent testimony before a parliamentary committee.

Three members of the volunteer organization told the House of Commons subcommittee on human rights that they fear the Russians would try to kill them.

"The White Helmets are the first witnesses of any violations of human rights in Syria," Nidal Ezeddin, who sits on the group's board, testified on March 29.

"This has annoyed the regime, annoyed their allies. For this reason, the allies made us their first target. We are doomed to die in any operation held against the people."

Ezeddin, speaking through a translator throughout his testimony, said they hunt for survivors in bombed-out towns and cities, but they are treated as enemies of the state.

"We are perceived by the regime as terrorists," he said.

Evidence put volunteers on 'collision course'

A Canadian Security Intelligence Service report, compiling the views of academics, referenced Russia's contempt for the White Helmets.

It noted Moscow's disinformation campaign directed at them.

"As became particularly clear during the siege of Aleppo in 2016, eyewitness evidence could discredit the Russian and Syrian attempts to militarise victims; airstrikes were hitting civilian buildings and civilians were dying," said the report, dated February 2018.

"In response, Syrian and Russian officials began to attack the credibility of such witnesses. One of the most important witnesses to the suffering was the aid organisation initially called Syria Civil Defence, later dubbed the 'White Helmets' after its staff's trademark headgear."

Trudeau asked the Israeli military to help out in a Syrian rescue effort. 6:49

The study noted the volunteers "increasingly became a main source of evidence of the true nature of the bombings, posting GoPro footage of airstrikes" and alleged human rights violations.

"This put them on a collision course with the government and its allies," the CSIS report said.

There are, however, groups, including the Montreal-based Centre for Research on Globalization, that have attacked the White Helmets, claiming the volunteers embed themselves with terrorist groups such al-Qaeda and the Islamic State in Iraq and Syria (ISIS).

Supporters have denied the accusation, but conceded the group is required to negotiate with extremists to get access to civilians in rebel-held territory.

Munier Mustafa, one of the volunteers who addressed MPs last spring, said they work in areas not controlled by the regime.

"Civil defence is very independent," he said. "This is a very good aspect, because we can do our work without being involved with any political party or military organization."