The Battle on the Tower
Harry Potter and the Half-Blood PrinceDeath Eaters infiltrate Hogwarts, leading to a fierce battle in the corridors and on the Astronomy Tower, where Dumbledore is killed.
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Bearing strength in each event
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The Infiltration

The Entry
The Passage
Draco Malfoy has repaired the Vanishing Cabinet, creating a passage from Borgin and Burkes into Hogwarts. Death Eaters, including Fenrir Greyback, Amycus and Alecto Carrow, and Thorfinn Rowle, enter the school.
The Engagement
The Order of the Phoenix, including Remus Lupin, Nymphadora Tonks, and Bill Weasley, confront the Death Eaters. A fierce battle erupts in the corridors. Spells fly, and the castle is damaged.
The Casualties
Bill Weasley is attacked by Fenrir Greyback and severely mauled. Neville Longbottom and Professor Flitwick are injured. The fighting is intense and chaotic.
The Blocked Stairs

The Resistance
The Barrier
Some Death Eaters block the staircase to the Astronomy Tower with a curse. The Order members cannot break through. Neville Longbottom tries and is thrown back.
The Escape
Severus Snape arrives and runs through the barrier as if it is not there. He joins the Death Eaters on the tower. The Order realizes too late that Snape is with the enemy.
The Aftermath
The battle continues below while Dumbledore is killed above. The Order is overwhelmed. The Death Eaters eventually escape, leaving destruction behind.
The Death of Dumbledore

The Murder
The Confrontation
On the Astronomy Tower, Draco Malfoy disarms Dumbledore. Dumbledore tries to reason with him. Then Snape arrives and kills Dumbledore with the Killing Curse.
The Fall
Dumbledore's body is blasted over the battlements and falls to the ground. The battle below ceases as the Death Eaters flee. The Dark Mark disappears.
The Aftermath
Harry Potter is freed from the immobilization spell and chases the Death Eaters. He confronts Snape, but Snape escapes. The battle is over, but Dumbledore is dead.
late June, the night of the invasion
late June, during the battle
late June, the climax of the battle