In Animal Farm, what happens during the battle of the windmill?

After
toiling very hard to rebuild the windmill with walls twice as thick as before, the animals hear
rumors that Frederick is planning to attack it. At first, the pigs downplay this idea,
becausehas been secretly negotiating to sell timber to Frederick, the Hitler figure in the
story. However, after Frederick takes the timber and cheats the animals out of the payment for
it, Napoleon goes on high alert. He places sentinels all over the farm.

The
attack comes. Frederick and his men are able to drive the animals back. The men dig a hole near
the windmill and pack it with explosives. They then blow the windmill up.

This devastating blow causes the animals to explode with anger and a desire for
vengeance. They rally and aggressively attack Frederick and his men, driving them off the
farm.

After the men are gone,wants the animals to celebrate the victory of
the Battle of the Cowshed. , however, wonders,

"What
victory?" . . . His knees were bleeding, he had lost a shoe and...