It started with thousands of people on the streets. It has resulted in millions of people on the move.

Two years after the Syrian uprising descended into the hell of civil war, the country has generated the world's gravest refugee crisis in a generation. Almost 2m people have fled the country; perhaps twice that number are uprooted and homeless within Syria itself. In total at least a quarter of the country's people have been driven from their homes.

They include Um Munaf, who lives in a camp in Turkey with her six children. "We are happy we do not hear the sound of the shells any more and we feel safe enough here," she said. "But what really worries me, as well as other refugees in the camp, is how long we will be staying here. Is Syria going to be liberated soon or in a year or more? Will the Turkish keep us for long or will we be a burden on them and they want to get rid of us? Am I going to see my house again and what will be the future for my children?"

They include Munaf Obeidi, whose family fled the Iraq violence in 2005 for Syria, only to find their situation suddenly much worse in their country of refuge. "I and my wife went to the UN looking for a country that would accept me with my family and we were told that we can go to Britain. But soon the British embassy was closed in Syria and we got nothing."

They include Hassan Bakar, who has not been able to escape, but has been almost permanently on the move within Syria, trying to avoid the unpredictable shifts in the frontline and sudden outbreaks of violence.

"Our house was shelled by many mortars and death was so close to us," he said. "We decided to flee through groves to Mua'adamiyat al-Sham on foot. There were seven of us – me, my parents and four brothers. We could not believe what we saw. Bodies and people fleeing everywhere. The destruction was huge. We stayed in Mua'adamiyat al-Sham for a few days but soon it was under a huge attack too as the army kept progressing and chasing rebels."

The sheer mass of humanity on the move generates astonishing facts. The Zaatari camp on the Jordanian border is a teeming mass of wretched superlatives. In a camp opened one year ago for 60,000, more than 150,000 people now huddle. The continued influx has at times overwhelmed the camp's capacity to deal with the sheer number of refugees and their ever-increasing needs. It has also changed the calculations of political leaders, some of whom are predicting that the refugee crisis could permanently alter the demographics of Jordan and Lebanon, just as the Palestinian exoduses of 1948 and 1967 did.

Every day the camp costs $500,000 to run and relies on 350 tankers trucking in water and 300 removing sewage. It is already Jordan's fourth largest city, with bakers, dressmakers, maternity clinics and classrooms, shops and stalls. And its own shortcomings. There are many of those. Abu Alla and his four children crossed the Jordanian border with just the clothes they stood up in and now live in an empty caravan, idle and helpless. "The kitchens are six or seven kilometres away from my tent and when I get there I can hardly get enough food. I always end with few pieces of bread. We have to buy food too otherwise we will die but the problem is where do you get the money? I have not seen anyone coming here to help us," he said.

In Lebanon, the numbers are no less dramatic. About 600,000 refugees have crossed the border, and if numbers keep rising it is estimated that by year-end one in four people in Lebanon will be a Syrian refugee. Another 400,000 have crossed into southern Turkey.

The potential for destabilisation is considerable: in the car bombs that killed more than 50 people in the Turkish city of Reyhanli in May; in the sheer numbers overwhelming Lebanon and Jordan, where everything from housing to local services to jobs markets are affected; in the sudden xenophobia afflicting refugees in further-flung countries such as Egypt and Greece.

Remarkably, there are people – tens of thousands of them – who have decided that Iraq represents a safer option than Syria. Here, the complaints that echo around the camps are the same: food is scarce, the heat unbearable, the prospects dim to non-existent.

"Our financial status is horrible since we arrived in Iraq," said Hadiyia Ali, who lives in a camp with her four children in al-Qaim, near the Syrian border. "My husband has never been able to find a job. We can buy meat or chicken only every few months. Our daily meals are tinned cheese or tinned cream, which cost 500 Iraqi dinar [28p]. We have potato with rice for lunch or beans with rice. Dinner is tomato and cucumber. My children want better food but we can't get it. All we have is donated to us by the clerics in the mosques and tribal leaders."

Refugee stories are hard to project. There is an air of inevitability about the narrative, the wretched predicament of the victims, the horrible things that have been done to them. Even the word "refugee" tends to engender fatigue. We've heard it all before.

Only we haven't. The tales from Syria bespeak unimaginable brutality, the senseless destruction of what was, until recently, a relatively comfortable place to live, work and raise a family. Now children are butchered, or left to fester with post-traumatic stress disorder in foreign countries that do not want them. Women sit through the days with listless offspring and absent menfolk, trying to blot out the violence – often sexual – that they have left behind. Authorities complain about the enormous cost, still woefully underfunded, of looking after millions of people who suddenly have nothing.

No one knows when it will end.

The Guardian wanted to do justice to the untold stories of these millions. We spoke to dozens of people – in Turkey, Jordan, Lebanon, Iraq and Syria itself, not to mention those further afield in Egypt, Greece and even the UK – to build up a picture of what it is to be suddenly bereft. On Thursday we will devote a day of coverage to the situation in the camps and cities of neighbouring countries, as well as the plight of those still stuck in Syria.