Germany's last stand
Summer, 1768 A.D.: The Greeks warn Sweden that continued relations with England will put their two nations at odds.
I saw this coming. Greece and England don't get along. Actually, Greece doesn't get along with much of anyone anymore. The Danish don't particularly like them, but they don't like me, either. If Greece starts a war, I will only be able to count on the Celts and my overseas allies for aid, and Greece might be strong enough to wipe us all out. And that's assuming they don't also get the Danes on their side.
Meanwhile, Greek forces overwhelm the city of Munich, putting a final end to the scrappy German Empire. Greece's borders now extend to the south end of Denmark and Austria, claiming nearly half of the continent's land area.
Winter, 1768 A.D.: As the threat of Greek hegemony grows, the Swedes invent the first rifled firearms. Far deadlier and more accurate than smooth-bore muskets, the Swedish army begins phasing out an infantry weapon that was already ahead of most of the world. The first rifle regiment are the Swedish Royal Guard, trained at the prestigious Stockholm military academy.
Hell yeah, Caroleans! I can now build Sweden's unique infantry that heal hitpoints every turn, even if they took another action. Perfect for brute-force, protracted campaigns. To give you some idea of how technologically supreme my military is, these guys are about equivalent in power to World War I infantry... while the Celts, for one example, are still using mostly Pikemen and Longswordsmen.
Next stop on the tech tree is Scientific Theory, which will improve my production and Science yields by allowing me to build public schools.
1776 A.D.: A renewed Defensive Pact is established between the Celts, the Greeks, and the Swedes, forming the New Continental Alliance.
It may seem odd, but right now, being friends with Greece is a good plan. I've decided that eventually stomping them into feta-scented dust is not going to be optional if I want any hope of winning, but the more time I have to extend my tech lead and build a sprawling campaign army, the better. I'm also getting free Great Person points for being friends with them, so in a way, they can only harm themselves by continuing this alliance.
A Celtic spy steals some texts on astronomy from Sigtuna. Sweden confronts the Celtic queen with this, and she apologizes, agreeing to bar her operatives from working on Swedish soil.
The Swedish spy network is the laughing stock of the intelligence community. They have never stopped any action of a foreign agent, and only about half the time are they even able to identify the thief. I suppose subtlety is not our strong suite.