Herrick District Library has a large amount of genealogical resources for those doing military research, especially for the the Revolutionary War, Civil War, World War I, and World War II. We have lists of local veterans, and also books and other resources with local information. We have guides for all of these wars listing what is available. There are also websites listed for military research.
For a quick place to start, check out the graphic below for an idea on which war your ancestor may have served in based on his birth date.
If you are looking for more information on a veteran, the National Archives is the place to look. The website has a huge amount of information, and you are able to request records through the site. There is a charge for records.
As always, if you have questions, contact the Information Desk at the library for help.