Massacre in King's Landing

"Orders are orders."

- Lord Janos Slynt to Tyrion Lannister

The Massacre in King's Landing was an event during the War of the Five Kings. Acting on King Joffrey's orders, the City Watch of King's Landing led by Lord Commander Janos Slynt tracks down and murders all of the bastard offspring of the late King Robert Baratheon.

In the books
In the A Song of Ice and Fire novels, the massacre of Robert Baratheon's bastards is ordered by Queen Regent Cersei Lannister shortly before the arrival of Tyrion Lannister to the capital. This was not the first time Cersei ordered the death of a bastard child of her husband; a pair of twins Robert fathered on a servant at Casterly Rock had previously been murdered.