On higher difficulty levels (immortal/deity), is there ever a good reason to mass attack with, say, infantry and artillery? or fighter planes? or non-nuclear missiles? Or is the post-cannons-cavalry-riflemen-era the point where you just beeline nukes or consolidate your diplomatic situation and go for space victory or diplomatic victory? For safest conquest/domination victory, should you just stop teching entirely once you hit rifling and steel, and take over the world with mass drafted rifles, spending gold on upgrades or unit purchases through universal suffrage, and leaving tech at 0%? At what point do you go for nukes and at what point--if any--do you go for later military units other than nukes?