After four-plus years of fighting, Syria's war has killed at least 250,000 people and displaced 12 million people. And, though it started as a civil war, it's become much more than that. It's a proxy war that has divided much of the Middle East and has drawn in both Russia and the United States. To understand how Syria got to this place, it helps to start at the beginning and watch it unfold:
Something important you'll notice: As more outside groups get involved in the war, each escalates by backing their side, and then a rival will also get involved to back the other side. So what you have is not just the Syrian factions escalating but regional and global powers escalating as well, thus worsening the war and entrenching Syria's divisions.
You'll also see that the countries getting involved don't always have the same objectives, and can end up working against even their allies. When Gulf states begin funding Syria's rebels, for example, they are mostly seeking to topple Bashar al-Assad and set back his patron, Iran, so they often fund extremists, believing they're better fighters. And different Gulf states fund different groups — at first Qatar is the most active, then Saudi Arabia — that are sometimes at odds with one another. And so on. These internal contradictions are an important part of understanding how the war has gotten so bad.
For more, read our brief history of Syria's war, from the rise of the opposition to the refugee crisis to why the US and Russia ended up intervening.