Israel's formally declared war on Islamist group Hamas - after a weekend of violence that saw 11-hundred people killed.
Militants attacked southern Israeli towns, killed 260 people at a music festival, and took dozens of hostages.
In response, there have been hundreds of strikes overnight on targets in the Gaza Strip.
Sky's Dominic Waghorn's in Ashkelon - where he says Israeli forces are being frank about how long the fighting is likely to last:
"What the Israelis say is that this is a very different situation to what they've had in the past in scope and scale, and that we should expect a long and hard conflict in Gaza itself. They say this is full on war".
