The help file in the Guardian section in game is pretty thorough, but I can't find an answer to one set of questions.. of course the answer may be somewhere else, but if so, I'd appreciate being directed to it.

In any case, most Guardian bonuses are pretty straightforward.. they apply to the units you send them with, or they apply to your defensive units they are defending with. But with capitals, either attacking (if a grouped attack), or defending (always), there are units of other members of your coalition with you. Do your Guardian bonuses help everyone attacking or defending with you, or just your own units? And for defending one's capital, can you send more than one Guardian to defend the capital (on separate trips, obviously)? If so, are bonuses of each guardian added together? If you can't send multiple guardians, can each member of the coalition send one? And if so, same follow up question: do all the guardian bonuses get added together for all units, or does each guardian only benefit the units of the player the guardian is associated with?