It took a graphic photograph of a dead child washed up on the Turkish shores for much of the world to finally wake up to the human catastrophe of the Syrian refugee crisis. That crisis is not new: More 4 four million Syrians have been forced out of their home country since fighting began there in 2011. Many were hastily resettled in squalid refugee camps in neighboring countries. Since then, thousands of these refugees have risked drowning in the Mediterranean in hopes of finding a better life in Europe.

This tragedy may seem incomprehensible — and, morally, it is. But to understand how things came to be this way, here are a few maps and charts that help to outline the very basics.

1) The number of Syrian refugees has been growing steadily for years

The above chart tells a very clear story: The Syrian civil war has been pushing civilians out of the country for three and a half years, and especially rapidly since the beginning of 2013, when the war became even more horrible than it had already been.

The Syrian uprising began in March 2011, as a broad-based nonviolent uprising against President Bashar al-Assad's corrupt, sectarian, and authoritarian regime. The Assad regime responded to these demonstrations by slaughtering protestors in the street. Eventually, perhaps naturally, they took up arms to defend themselves. By the beginning of 2012, the uprising had become a civil war.

The war escalated very, very quickly. In March 2012, the UN estimated that around 9,000 Syrians people had been killed in the fighting. In January 2013, the estimate was up to 60,000; then 100,000 by July.

2) The war in Syria is devastating for civilians

The dynamics of the Syrian civil war are particularly awful for civilians. As you can see in the above animated map, a collection of Thomas van Linge's maps showing areas of control from March 2014 through September 2015, the borders have shifted frequently between multiple groups. This has meant that the front line has, at one point or another, come to many, many Syrian towns and neighborhoods. Indeed, much of the fighting has been over control of civilian populations — a war that both Assad and ISIS have waged by targeting those civilians themselves. And it has meant that any given family might have lived under the distinctly horrible tyrannies of multiple factions.

The Assad regime, for its part, has deliberately targeted Sunni civilian population centers, both to undermine the rebel base of support and as part of a devilish plan to sectarianize the conflict. His weapons have included sarin gas and barrel bombs, which are barrels filled with explosives and dropped indiscriminately from helicopters.

To make matters worse, ISIS has taken large swaths of Syria — and forced the people who live under their rule to abide by its horrific system of Islamic governance. ISIS, as well as other extremist Sunni groups, have targeted minorities and other civilian groups for systematic terror and murder. It makes sense that this war would cause people to flee in huge numbers.

And the conflict is still raging, with no end in sight. Stephen O'Brien, the UN's undersecretary general for humanitarian affairs, said in August 2015 that more than 250,000 people had been killed over the course of the conflict. So long as this continues, there will be millions of Syrians unable to go back to their homes.

3) Huge refugee populations are straining Syria's neighbors

As Syrians are pushed out of their homes, they have to go someplace. And most have ended up in camps: internally displaced persons (IDP) camps within Syria or refugee camps in neighboring countries such as Lebanon, Turkey, and Jordan. These countries are being stretched to their limits by the influx, with both the host countries and of course the refugees themselves suffering under the burden.

In total, about half of Syria's entire population has been uprooted by the fighting. For many of them, there's no home to go back to.

Lebanon's population in 2013 was about 4.5 million; the roughly 1.2 million Syrian refugees have increased its population by about a quarter. Jordan has taken the equivalent of about a tenth of its 2013 population. Even Iraqi Kurdistan, itself currently in the midst of a war against ISIS, has managed to take in more than 200,000 Syrians. These huge population influxes are extremely difficult for local governments to deal with. The camps absorb lots of resources, which local governments might not have much of, and can be politically destabilizing.

Amnesty International, citing UN figures, reports that "at least 40% of refugees [in Lebanon] live in inadequate accommodation ‘including in makeshift shelters (garages, worksites, one room structures, unfinished housing) and informal settlements’ whilst ‘others are at risk of eviction or live in overcrowded apartments.’"

The funding is insufficient. The UN High Commission on Refugees (UNHCR) is about $3 billion short on its 2015 funding requirements for Syria operations. In December 2014, the World Food Program declared that it had to stop providing food to 1.7 million refugees — because it didn't have enough cash. An emergency fundraising drive restored that program, but the episode illustrates just how precarious the situation is for aid organizations trying to help Syrian refugees.

Bottom line: The regional response system is overloaded, and Syrians are suffering. Even if the camps were better funded, they're still camps, and the future they offer Syrian families is not bright. That's why these families are increasingly fleeing the region altogether.

4) Syrian refugees are increasingly traveling to Europe — at tremendous risk

Syrian applications for asylum have spiked in the past year and a half, reflecting a turn among Syrian refugees towards Europe as safe haven.

"They may have been in Jordan or Lebanon or Turkey or have been in transit somewhere for a couple years and are now moving onward," the head of a European aid organization told BuzzFeed's Borzou Daragahi. "It’s a sign of immense desperation in the areas where they sought refuge. They have these nice camps, but there is no hope."

According to Daragahi, the breakdown in Syrian peace talks, as well as growing fears of conscription into the Syrian army as it weakens, have helped to push people out. A lack of job prospects has made life in the camps untenable; Syrian refugees are legally barred from some jobs in Jordan and Lebanon.

Europe is thus the only real choice for a future, but the trip is dangerous. Roughly 332,000 migrants have tried to reach Europe from the Mediterranean Sea this year, according to the International Organization for Migration (the UN estimates that about half of Mediterranean Sea migrants are Syrian). At least 2,636 of the total have died — meaning one in every 125 Mediterranean Sea migrants will die attempting to get to Europe.

Those are daunting odds, especially given how few of these refugees have actually been permitted to have real lives in Europe once they get there. The fact that people are even attempting this tells us just how bad the situation in Syria and the Middle East has gotten — and suggests that maybe, just maybe, it's time to start letting more refugees into our own country.

Watch: The shameful US response to the Syrian refugee crisis, by the numbers