It was the Mouse King's army.
3 seconds sound clip from the Barbie in the Nutcracker movie soundboard.
You can hear this line at 00:27:36.045 in the DVD version of the movie.
Quote context
[...]
- Ow! Hey.
- It's all right, they're just children. With very good aim.
- Wait. We found this, is she yours?
- Patti!
- We went out with Marzipan to gather candle berries. We came back and everything...
- It was the Mouse King's army.
- This is all Prince Eric's fault.
- The son of the King who ruled before the Mouse took over.
- Yeah, but he wasn't much of a Prince.
- The King left his throne and the golden scepter to his royal advisor... The Mouse.
- Until the Prince could prove himself worthy.
- Let me guess. The Mouse decided he liked being king.
- But what happened to Prince Eric?
- We're better off without him.
[...]