When introducing an acronym, is the acronym pluralized in the first parenthetical use? For instance request for forces is RFF, the first time I use it I spell out "request for forces" followed by (RFF) for use in the rest of the document. Since "forces" denotes plural, do I include the "s" in the initial parenthetical i.e. (RFFs)?
You have to decide whether to include the S when you're introducing the term, based on what you're planning to do with it later. If the S will be helpful some of the times you'll use the acronym, then yes, include it. If the only way you'll ever use the acronym is to refer to "request for forces," then omit the S.
I suspect "force" will always be plural. However, I can imagine that one might want to talk about multiple such requests. In that case, RFF (one request) and RFFs (requests, i.e. more than one request) would be slightly different.