"All gave some, but some gave all."

Im not sure of the direct origins from that saying, but it is commonly used in the presence of POW/MIA memorials and such, and I assume could be considered an "unofficial" motto to the subject. You may want to check http://www.ojc.org for more details.

and I assume could be considered an "unofficial" motto to the subject

I think so to.
I have tried to search for the origin of the quote, but i can't find anything.
I have heard it in many languages, and it refers not only to POW/MIA but also to KIA. (to the ones who "gave all")