Raqqa is the capital of ISIL’s so-called caliphate, and it’s probably where the group will make its last stand.

The Syrian Democratic Forces (SDF), the United States’ closest ally in Syria, has begun the final push for Raqqa, one of the last and most important strongholds of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS).

Most routes to the city have been captured by the US-backed forces, and ISIL is losing ground day after day.

READ MORE: The battle for Raqqa explained

The SDF has been working to encircle Raqqa since November in an offensive backed by the US-led coalition that is also fighting ISIL in Iraq, where the group is on the brink of defeat in the city of Mosul.

The US-led coalition has said 3,000 to 4,000 ISIL fighters are thought to be holed up in Raqqa city, where they have erected defences against the anticipated assault.

For months now, ISIL has been preparing for the offensive on Raqqa. After the coalition destroyed all bridges across the Euphrates, ISIL started digging trenches across the city and putting barricades.