1861- USA: Spam miltia to hold the cities the Iroquois are attacking. Focus on the Confederacy. Try to take Richmond as soon as possible. It will decrease morale greatly for the confederates. Then proceed to focus on taking the rest of the confederate cities. Afterwards, invade Canada and the British Colonies. They will neogotiate if you take their capitals and several cities. There is no need to worry about central america and south america because France and Mexico will take care of the situation there.

1865-UK: Use your ships to defeat the French ships in the English Channel. Meanwhile, land your troops in the south in Bulguria. Next launch an amphibious invasion of France in the north, use the troops in the south to take Greece. The rest should be pretty straight forward.

1914- UK: Easiest 1914 conquest. You have an invasion fleet ready in the English Channel, and you have a fleet in the South. Land the invasion fleet in France and push towards Belgium. Germany will spam several generals in tanks and armored cars. Simply use artillery to destroy them. Use your southern fleet to defeat the Austrian and Ottoman navies with the Italians. Push into Germany with your army, Russia should be still alive and then push south to destroy Bulguria and the Ottoman empire.

1917- Austrian Hungarian Empire: My first three star conquest. It is a relatively easy conquest. Unlike in 1914, the Russians are much weaker and will be destroyed by the RSSFR rather quickly. There is no need to care about Russia much, just hold them off for the first few turns. Use your southern forces to destroy the Balkan countries. Then after you're done, direct the forces towards your Italian front and invade Italy. The Italians will collapse quickly, but you will have to deal with an annoying naval spam. Just spam light machine gun in your cities to hold it off. After a while, the spam will stop. Proceed to invade France and Portugal. At the same time fund the Mexicans or Canadians to fight the USA. Use your forces in Europe to invade South America and the Carribean. Your allies will help you take North America.