Jabaliya refugee camp has the toughest of reputations. It was in Jabaliya's crowded alleyways that the first Palestinian uprising broke out. In this second Intifada it has been a stronghold of groups like Hamas.
Jabaliya is burying its dead
And now the Israelis have fought and battered their way into the heart of the camp.
The army's snipers are taking their deadly aim from several high buildings. And troops in tanks are in control of a school at the end of the market place.
Mid-afternoon on Thursday I saw many people in the streets there.
There were fighters - some in masks and all of them armed.
One group was setting up what appeared to be a mortar in the middle of the road. But the great majority of those in the streets were civilians.
Many were children and teenagers excited by the action - and peering dangerously around the school walls at the soldiers.
An hour or so later a tank fired into the crowded market place. Seven people were killed - including a 14-year-old - and more than 20 injured.
An ambulance man said the street had been full of civilians.
The Israelis said they had been returning fire at a militant target.
I was at Jabaliya's hospital when the casualties arrived. Some of the bodies on the stretchers were just a mass of blood and torn flesh.
Every few minutes the ambulances brought more dead, or dying or badly wounded. And every time there was pandemonium as the medics tried to rush the casualties through a crowd that had gathered at the hospital doors - desperate for news of those inside.
I saw a shaken-looking Hamas fighter, standing with the bloodstained clothes of a friend he had just brought to the hospital.
And I saw a woman rush into the courtyard, screaming and slapping at her face as she ran.
Someone she loved was dying or about to die. Later I saw her weeping as she walked slowly out of the hospital gates.
Israel has had its casualties too.
Late on Wednesday a Hamas rocket crashed down on the town of Sderot - which lies in Israeli territory, a few kilometres beyond Gaza's boundary.
The missile exploded close to two children, who were playing outside their grandmother's home. Both of them, a two-year-old and a four-year-old, were killed.
It is attacks like these that this Israeli thrust into northern Gaza is aimed at stopping. Hundreds of rockets - known as Qassams - have been fired into southern Israel.
Israelis mourn the victims of Hamas rocket attacks
The missiles are crudely made in workshops in Gaza, and for a long time they were largely ineffective - little more than a nuisance.
Now though it seems the rockets have been made more powerful, and more deadly.
Israel says that no nation could tolerate the random shelling of its civilian areas.
Prime Minister Ariel Sharon is reported to have ordered the army to do whatever it must to end the missile threat from Gaza.
Hamas justifies the attacks by saying that it is fighting an occupation. It wants an Israeli withdrawal not just from Gaza and the West Bank.
Hamas says that Israel itself is on land that rightfully belongs to the Palestinians - and it has sworn to fight for all of it.
Ariel Sharon says he wants to withdraw from Gaza next year - ending nearly 40 years of occupation.
The militants here want to make any such Israeli pullout look like a retreat under fire. The missile strikes are a way of doing that.
Hamas is likely to do everything it can to keep launching its Qassams at Sderot.