Ludwig was from Kaiserslautern, GE and said he was in the German Army. He was old enough for WWII, but not completely sure about when he served. He immigrated to USA in March 1957.
With this year of birth it is very likely that he served. Drafting for this year began in October 1938 and more than a third of the drafted servicemen died.
The service record should be available from Deutschen Dienststelle (WASt). This is your primary source for this kind of requests. Please see details for making a request here: Finding information on German soldiers from World War I and World War II?. You are entitled to make a request if he is your ancestor. In case he is some other family member, you need a permission from his descendants to make a request. On the form (https://www.dd-wast.de/en/tracing-request/private-matters-research.html) you should pick all options as “purpose”.