Why should they feel they have to? You'll tell them what they need to know, as gamemasters always have to, and who cares how many things they don't need to know that has been published?...none of my players are interested in reading the corpus of "Traveller Lore" either from my Library or from what they can find online (and then have to sort through canon and non-canon material). Plus they'd have to figure out what time I'm setting it in, then find the right materials.
Every player I know is willing to adventure in historical settings despite the "spoilers" that Real World history can provide. For one thing, they never know for sure if I'm going to stick to history or will let things develop out along a tangent. Perhaps the PCs can prevent the War of 64 from turning out so disastrously for Denmark.Then, beyond that, I don't know many players that are that interested in playing a game with a "foregone" (sp?) conclusion - that's the real problem with TNE, who cares about the 5FW when everything is going to wiped clean in less than a hundred years anyways...
Mostly, though, the adventure will be on a scale where historical knowledge will just provide interesting background. Who cares if the Swedes are besieging Copenhagen? What does it matter that the players know that the siege won't be successful and that the PCs won't make a difference to that? It's the half-company of Swedish dragoons stationed in the local manor house that is the problem to be overcome.
I vehemently disagree that this has to be a problem. Regina Starport, the beginner campaign I and some other people wrote for JTAS Online, is set in one small (albeit very populated) part of one huge metroplex on one single planet in one single subsector in one single sector in one single domain in one single Imperium in Charted Space. And there are plenty of ways for the PCs to make a difference. In Regina Starport, that is. Why is it a problem that what they do don't make a difference to the rest of Regina, the Duchy of Regina, the Spinward Marches, the Domain of Deneb, the Imperium, and Charted Space?The OTU, as portrayed, as succeeded in doing the one thing that every campaign should strive to avoid - make players feel like what they are doing is utterly irrelevant to the good of the setting.
Hans