 He served under Rosecrans and McClellan in western Virginia.Ewing became colonel of the 30th Ohio Volunteer Infantry in August 1861.In November 1861, when his brother-in-law William T. Sherman was relieved of his command in disgrace, Ewing aided his younger sister Ellen Ewing Sherman in making the rounds of Washington D.C., denying sensationalist media claims that Sherman was insane, and personally lobbying the President for Sherman's reinstatement.