There was a lot of empty space so I started out with peaceful expansion. Roosevelt attacked me first, but I was prepared: protective archers, on a hill with city walls and he lost 15 units to my 1 lost unit (unlucky). IIRC, Lincoln piled on, but I was able to defend, but unable to punish the aggression until later. When I got to rifles, I moved on Roosevelt, leaving him with 3 cities in the SE corner upon vassalization. At the same time, I took 2 holy cities from Lincoln which were on my borders and agreed to peace. When I got tanks, I wiped out Lincoln from the main continent and vassalized him, also. Then a funny thing happened, Washington, who was my 'friendly' ally most of the game, piled on Lincoln just as I captured Lincoln's last city on the continent. In the screenshot you can see his stack of death. This was an opportunity to decimate Washington's army in the field, so I did that also on the same turn! (note: relation had dropped to 'pleased' so I didn't feel the least bit guilty about the backstab.) Washington's cities fell easily and domination was achieved in 1898.