While illegally crossing the border between Iraq and Syria, Peter Douglas, a Canadian, was adamant that his incursion was for humanitarian reasons — to help the people of Syria.

Douglas is one of a growing band of foreigners to dodge authorities and join the fight against the Islamic State militants who have slaughtered thousands and seized vast areas of Iraq and Syria, declaring an Islamic caliphate in the territory under their control.

Many of these fighters say that they are there for humanitarian reasons, but acknowledge that their decision to take up arms on behalf of the Syrian people will not be viewed as such by some.

“I want to fight the Islamic State, although it might be the last thing I do,” said Douglas, 66, from Vancouver, as he prepared to board a boat crossing a remote stretch of the Tigris River, which straddles the two countries.

“I know I have 10 years to live before I will start developing dementia or have a stroke so I wanted to do something good,” he added, although he acknowledged that taking up arms was new on the list of jobs and occupations he has previously pursued.

So far an estimated few dozen Westerners have joined Kurdish fighters battling the Islamic State group in northern Syria — a group that includes Americans, Canadians, Germans and Britons.

The Syrian Kurdish armed faction known as the YPG has not released official numbers confirming foreign or “freedom fighters,” and academics say it’s hard to assess the total.

But the number pales in comparison to an estimated 16,000 fighters from about 90 countries that have flocked to fight under the banner of the Islamic State group since 2012, according to the U.S. Department of State figures.

The United Nations has warned that extremist groups in Syria and Iraq are recruiting foreigners on an “unprecedented scale” and with a commitment to jihad who could “form the core of a new diaspora” and pose a threat to the West for years to come.

Western governments are closely monitoring foreign fighters, but law enforcement agencies are taking a softer approach toward those who leave to join the Kurdish resistance than those who chose to do battle for the Islamic State.

British Prime Minister David Cameron has made it clear there is a fundamental difference between fighting for the Kurds and Islamic State. British law stipulates fighting in a foreign war is not automatically an offense and depends on circumstances.

Two British military veterans, Jamie Read and James Hughes, returned to England last month after several months with the YPG, saying they were fighting for “humanitarian purposes.” No action has been taken against them since their return.

They signed up after becoming outraged by a series of chilling videos documenting the beheading of U.S. journalists James Foley and Steven Sotloff, U.S. aid worker Peter Kassig and British aid workers David Haines and Alan Henning. They have also been moved by the plight of millions of Syrians caught between Islamic State militants and government troops.

The Syrian Observatory for Human Rights, a British-based monitoring group, estimates that over the past six months the radical Sunni group has killed about 1,878 people off the battlefield in Syria, mostly civilians.

In total, more than 200,000 people have died in the Syrian civil war, which started when President Bashar Assad’s forces launched a brutal crackdown on peaceful prodemocracy protests in 2011.

“We went there to help innocent people and to document the YPG struggle against ISIS,” Hughes, 26, who spent five years in the British Army, told reporters.

ISIS is the acronym for Islamic State in Iraq and Syria as the Islamic State group was formerly known as.

“We had a warm welcome home. Everybody thought we were heroes. They were proud of us. I also received hundreds of messages from people wanting to join the YPG,” he said, adding that he plans to return to Syria in the coming months.

Still, many foreign YPG fighters are concerned about legal repercussions when they return home, and seek to stay anonymous.

“We might get in trouble with our governments,” said one U.S. veteran who was careful to ensure that all his financial and legal affairs were in order before departing for Rojava, the area controlled by the YPG in Syria.

Many also harbor concerns at how the media portrays them at home and wanted to clarify that they are volunteers, not mercenaries, adding that their contributions are unpaid.

Many have some military experience and have signed up to fight through contacts on Facebook.

Lorenzo Vidino, an analyst at the Institute for the International Political Studies in Italy, said foreign fighters might argue they are joining the battle against Islamic State for the moral good, but their actual impact on the conflict is negligible.

“Westerners joining the YPG are a very small phenomenon especially if compared to Islamic State. The IS recruitment machine works better and you can see evidence of that in terms of numbers,” he said.

U.S. fighter Dean Parker, 49, joined after watching video footage of the Islamic State group’s onslaught on the town of Sinjar in northwest Iraq in August, when militants killed or captured thousands of minority Yazidis.

“I saw the fear and terror on this child eyes who was looking directly at me through the camera . . . I’ve never been moved by anything like that in my life,” he said in an email exchange, one of several foreign fighters from Syria interviewed on location, by email or by phone in November and December.

Canadian-Israeli woman Gill Rosenberg, 31, from Tel Aviv, said in a recent interview with Israel Radio that she decided to join the YPG for humanitarian and ideological reasons.

But not all foreign fighters are motivated by the same cause.

Jordan Matson, 28, a U.S. Army veteran from Wisconsin who joined YPG about four months ago, said he left because he was running away from a “civilian” life he didn’t really like.

“Here, instead, everything makes sense,” he told reporters at a YPG base near to Derik, a town in Syria’s northeastern Kurdish region.