A timeline of five years of Syrian conflict

SYRIA (Reuters) -  In March 2011, few people could have imagined what these protests in Syria's Deraa would lead to.

Five years on, no one disputes that the Syrian conflict has become one of the gravest crises on the globe.

It started peacefully enough... as mass protests against President Bashar al-Assad for the killing of demonstrators by security forces.

But Mr Assad's crackdown on protesters transformed their movement into an all-out armed insurgency.

Rebel factions eventually formed but those were increasingly overtaken in 2014 by Islamist groups, notably Islamic State (ISIS) - which introduced an unprecedented level of grim violence to the conflict.

In September of that year, US forces began air strikes on ISIS targets.

Many nations would join the US-led campaign against ISIS but in 2015, Moscow, Syria's ally, started its own aerial campaign in support of Mr Assad, complicating efforts to end the conflict on the military and political front.

The increased fighting helped unleash one of the largest human migrations in recent memory, as hundreds of thousands of desperate people pushed their way to anywhere they could find refuge.

Now, diplomats are resuming peace talks in Geneva, hoping a cessation of hostilities can transform into real peace.

But the sides show no sign of compromise over the fate of Mr Assad himself, meaning there's little ground for a negotiated settlement to end the conflict that's killed more than a quarter of a million people.