The circumstances were desperate. Thousands of Yazidis were trapped on a barren hilltop in northern Iraq, surrounded by Islamic State militants and desperate for food and water.

Many died of starvation and exposure before Iraqi security forces eventually broke the siege, backed by American air strikes.

In a speech to foreign diplomats last month, Foreign Affairs Minister Rob Nicholson said the siege on Mount Sinjar last August was a perfect illustration of the larger problem in the region. Those people needed aid, he told the group, but they also needed protection. "The two go hand in hand," he said.

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As Ottawa prepares to spend half a billion dollars on the military mission against Islamic State militants in Syria and Iraq by next year, non-governmental organizations are struggling to meet the basic needs of millions of people in the region. Canadian funding for humanitarian assistance has made a difference, but as the conflict in Syria enters its fifth year, organizations working in the region say far more help will be needed.

At the same time, aid workers are warning against drawing links between the expanded military mission and more humanitarian aid, saying their staff could face greater risks in the region if there is any perception their work is connected to a military campaign.

Nearly four million people have fled Syria since the conflict began several years ago. Many are living in refugee camps in neighbouring countries, placing additional strains on government services. Inside Syria the situation is even more severe: Some 7.6 million people have been forced from their homes but remain in that country, where humanitarian agencies are often unable to reach them; more than 200,000 people have died in the violence.

So far this year, Canada has offered about $50-million to the crisis, which is being directed to aid organizations helping people affected by the Syrian conflict. The government also committed $40-million to aid programs in Iraq in January, in addition to funding provided in earlier years.

An assessment of Syrian aid commitments by international NGO Oxfam says Canada's fair share for this year would be just under $180-million.

Ottawa did not promise any new funding at a recent pledging conference for Syria in Kuwait, even as the United States and Kuwait announced they would provide hundreds of millions in additional aid this year. The conference fell short of its goal despite those pledges, raising just over half of the $8.4-billion the United Nations says will be needed to help deal with Syria's crisis in 2015.

A spokesman for International Development Minister Christian Paradis said Friday that the government would continue to provide humanitarian assistance to people in the region.

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Ann Witteveen, who manages Oxfam Canada's humanitarian unit, said Canada has been a generous donor to the crisis in Syria and was among the best contributors during 2014. The $50-million Canada has committed so far to Syria is based on an assessment up to the end of March, she said, leaving the rest of the year for Canada to increase its funding. "We expect and hope that Canada will increase their pledges as the year progresses," she said in an interview.

Yet as the crisis in the region persists, aid organizations such as Oxfam worry that the international community will lose the motivation to provide the kind of funding that is so desperately needed. "I think the problem that we have with crises like this is that they just become so prolonged," Ms. Witteveen said. "So while people can be a bit enthusiastic at the beginning of a crisis, it's hard to really sustain enthusiasm."

Dave Toycen, president of World Vision Canada, agreed that Canadian assistance to the region has been generous. "But at the same time, we're just seeing expanding need in these areas," he said. "So obviously, from our perspective at World Vision, we are hoping there might be some way that the government can provide some more funding."

Canadian aid to the region so far has included funding for UN agencies, including the World Food Programme and the High Commissioner for Refugees, which are focused on providing food and essential relief items such as blankets, plastic sheeting and clothing. Other assistance includes counselling for survivors of sexual violence, provision of safe drinking water and support to hospitals and health centres.

Aid workers in the region have faced incredible odds.

Stephen Cornish, executive director for Médecins sans frontières (Doctors Without Borders) Canada, said some hospitals in Syria have been forced underground – into caves, farmhouses and basements – to avoid becoming targets. But that means they may also be hidden from patients who need those services.

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In one case, a woman was injured critically when a bomb exploded in her family's living room, Mr. Cornish said. She managed to get into a taxi, but the car drove right past a hospital because the driver couldn't see it. The woman bled to death before she could reach help.

Humanitarian workers say access to people in need is a critical concern inside Syria, but they are also careful to warn that access is not a problem that more military intervention can solve.

Last week, leaders from the Canadian Red Cross and the International Committee of the Red Cross published an article calling on Canadian politicians to ensure the political debate over the fight against Islamic State militants is kept separate from issues of humanitarian aid.

"Public debate that conflates political and military dialogue with humanitarian aid undermines the very principles that enable organizations such as our own to provide urgently needed relief in times of conflict," Conrad Sauvé and Yves Daccord wrote. "Those most affected by this crisis, and those who provide humanitarian assistance at great personal risk, cannot afford for neutral and independent humanitarian aid to be compromised."

Mr. Cornish, from MSF Canada, said that kind of connection occurred during the war in Afghanistan as governments tried to integrate aid, diplomacy and military objectives. "When you follow the discourse of all of the three main parties, they're talking about the political, military and the humanitarian all in the same sort of dialogue and narrative," he said of the conflict in Iraq and Syria. "So I think there is a risk that the lines could become blurred."

Bessma Momani, a professor of international affairs at the University of Waterloo, said the government has suggested in recent weeks that in order to help people in distraught regions of Syria and Iraq, Islamic State militants have to be defeated.

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"But when you look where [the Islamic State] is, those are not the regions where Canadian humanitarian aid was most concentrated, so it doesn't really hold water," Prof. Momani said. Eastern Syria and western Iraq were "never a part of their plan in the past 25 years, why is it going to be now?" she said. "Great if you want to commit [to helping people], much of these people are in refugee camps."

Prof. Momani said she remains concerned about Ottawa's long-term strategy in the region, including what the plan would be if the threat of Islamic State militants is eventually diminished. "The fear that I have is, okay, if you liberate Syria from [Islamic State] hands, you're effectively allowing [Syrian President Bashar al-]Assad to come back."

Both the NDP and Liberal opposition parties voted against the government's plans to launch air strikes in Iraq and later to expand them into Syria.

NDP international development critic Hélène Laverdière said she doesn't think the Conservative government has done enough to make humanitarian assistance a priority. Ms. Laverdière said she would like to see Ottawa come up with a plan that lays out long-term funding for a range of development issues, including good governance, democratic institutions, education and trauma healing.

Liberal foreign affairs critic Marc Garneau said he would like to see more funding for a co-ordinated humanitarian approach to the region.

Both parties have also called for Canada to accept more refugees. Ottawa has so far committed to settling 11,300 Syrian refugees by 2017, but many of those people will have to be sponsored by private organizations. About 1,300 have been settled so far, according to figures tabled in Parliament last month.

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"People who have lived a certain amount, and can remember [a large number of] refugees coming to this country, realize that for Canada this has been an act of generosity and it has made our country better," Mr. Garneau said.