What incident had just occurred on Animal Farm at chapter 7

Three hens, which had led the hen rebellion, confess that Snowball incited them to revolt in a dream vision. After this, several other animals confess to crimes both great (murder) and small (stealing). Napoleon has them all murdered. The animals were supposed to create a society of equality and freedom, not one of “terror and slaughter” (95). Still, Clover thinks Animal Farm is better than it was in the days of Mr. Jones’s rule, and her heart remains faithful to it. Unable to put her thoughts into words, Clover leads the animals in singing “Beasts of England.” That is when the song comes in. The song had once, under Old Major, represented freedom and animal equality. Now the song has lost meaning. Only Boxer thinks if they just work harder, things will be better.