Historical Leaders: Your country will receive any generals, admirals, explorers or conquistadors that it did historically at that date, but is unable to hire any, making tradition (and buildings, national ideas and modifiers that give it) useless. I believe (but am not sure) that this also makes national ideas and modifiers that change leader stats (manuever, shock, fire) useless as well, since historical leaders have set stats. Note that this feature makes Quest for the New World useless, since you cannot hire explorers or conquistadors (this may make colonization of the New World more historical). Like advisors, some countries are blessed with leaders while others never receive any, but keep in mind that your country is likely to receive many leaders during times that were historically bloody - you should plan your wars in advance (or take advantage of new generals appearing) if you want to make sure of having leadership in your wars. Note that countries that did not exist historically will not receive any leaders at all, so if England becomes Great Britain in 1500 it will not receive any leaders - including explorers - until 1703, thus crippling itself.