65th Ind. Infantry had taken part in the Atlanta campaign and battles of Franklin and Nashville, Tenn., all required hard service so by January 1865 he may have just had enough.
Problem(s) at home, poor medical care, are other possible reasons for desertion

There was a John Dew, private, Company K, 154th Ind. Infantry of Montgomery County, Ind. (March 1865 enlisted-Augusut 1865 mustered out).

Other choices are 18th and 30th Ohio Infantry Rgts., 42nd and 93rd NY Infantry, 62nd and 145th Illl. Infantry and 7th Md. Infantry