Mexican War Records

I am trying to track down records on an ancestor that according to his obit he fought in the Mexican and Civil War.

His name was Thomas McIntosh.  He was born in 1825 in Massachusetts and died Dec 7, 1907 and is buried in Lodi, WI.

I have found information on his Civil War service - Wisconsin 3rd infantry, but having trouble with the Mexican War.

Any suggestions would be great.

Thanks

Dawn C