Too many variables in your question. For starters, it's not a "given" that "battlefields are off-limits". Oh sure, perhaps the federal parks "obvious historic landmarks" types ones (ghettysburg, shiloh, etc...). But no, not all "battlefields". There can be battlefields where currently other types of land are: City or county or state lands where it's not "parks" and no such restrictions/laws exist. Or private farmers fields, and so forth.
So you'd need to specify the the type of entity who has the battlefield to which you speak of. And also: to simply say "federal" or "state" etc.... is also ambiguous. Not all "federal" land is federal "park" land. And not all state land is state parks land, and so forth. Road right-of-way is an example of another type of land, etc...
And as Jay points out, variables like "navigable" come into the picture. And someone can get super detailed and debate whether that mean you'd have to be "in the water" (as opposed to walking the shore-line), to avail yourself of such things. And then debates about how far back from the water's edge, blah blah blah blah. It gets absolutely ridiculous if you want to knock yourself silly asking Q's.
So let's just cut -to-the-chase, and assume that your site is not directly adjacent to some sacred historic monument type park, right? Well then in that case, does anyone really care? And even if someone did say something, you're looking for the boy-scout ring your dad lost there when he was a kid, right?