The Israeli nerve centre watching Gaza's every move

A group of Israeli soldiers is gathered round a television screen. They are watching the grainy images of a youth crawling towards the perimeter fence that hems the Palestinians inside the Gaza Strip.

The dark form tracked on camera is placing a bomb by the fence. Minutes later, his body is shaken by tank fire. A second shot confirms that the militant is dead, and his bomb activated.

We are inside the Nahal Oz military base on the border with Gaza. With the help of a white blimp bristling with cameras, and remote-controlled drones that buzz overhead, the Israeli military have every square inch of Gaza under surveillance.

At Nahal Oz, the headquarters of the southern command which monitors Beit Hanoun and the rest of northern Gaza, the cameras watching the nearby fence pick up every sound.

Palestinians have been warned that if they approach within 300 yards of the fence they are risking their lives. The sensors along the fence can tell the difference between a human and an animal if it ventures into the no-man's land where Palestinian crops and orchards have been flattened. A low throbbing alarm goes off if the sensors are activated.

The moment a Qassam rocket is fired towards Israel, a siren sounds inside the army base. The soldiers know they have 12 seconds before the notoriously inaccurate missile reaches its target, usually in the town of Sderot.

"If a Qassam is fired, we don't fire back straight away because of the possibility of hitting civilians," says a second lieutenant who identifies herself as Hila. "It goes through a lot of levels before we have permission to fire."

On a quiet day, some seven or eight rockets come over the fence. But when tensions are running high, as during the Lebanon war, up to 70 missiles are fired against the Israelis. "They know where we can fire, and where not, so they deliberately choose places where we cannot retaliate," the officer says. In one case, Palestinians fleeing Israeli fire took refuge in a petrol station.

On the army base TV screens militants can be seen using children to place their home-made bombs in an attempt to avoid reprisal gunfire. The fighters are also accused of storing weapons on the first floors of houses, where civilians living in downstairs rooms risk bearing the brunt of Israeli missile strikes.