Military patches have been in use for many years and originally were used to identify individuals to a specific military unit. Over the years, that original purpose of a patch still remains but the actual usage has evolved to include patches for higher and larger military entities as well as having several different patches for different uniforms.
Anyhow, this web-page focuses on Skivvy9 at Osan but since there are lots of related patches, they are now broken into the categories below.
Enjoy.
6903rd only (Squadron, group, etc).