Headquarters, Company 1, Ordnance, don't know what CAS means, Battalion.

Do you know what he did? If so, it can probably shed some more light. I'm an active duty guy. Shoot me a PM and let's see if we can get you in touch with the Army's center for military history.

/r/military might be a good place to ask, if you don't find sufficient answers here

For what country did he fight?

Hello there! As your question is related to looking for identification/information regarding military personnel, our Guide on Military Identification may be of use to you. It provides a number of different resources, including how to request service records from a number of national agencies around the world, as well as graphical aids to assist in deciphering rank, unit, and other forms of badges or insignia. While the users here may still be able to lend you more assistance, hopefully this will provide a good place to start!