Answer: They were asked to help the Ming defend against the rebels.
Explanation: This is because Manchu become involved in China’s peasant uprising because they were involved in the wars fought against the rebels. They fought various fights against rebellions and make great contribution in defending the Ming dynasty. These rebels has a great threat to the Ming dynasty and if they were not stopped, the Ming dynasty should collapse and lose its control on china and the rebellions would rule all over china.