Article: In Empire: Total War, there are two types of nations: Major and Minor. Minor nations usually only have one city, but can still field impressive armies if given enough time. Find the Minor nations nearby your starting point and mark them as your first targets.  If you give the minor nations too much time to build up their armies, they can pose serious threats and significantly slow down your expansion. You can use Minor nations as a way to grind for more XP for your troops. Keep attacking the single city, letting the nation rebuild between each attack. This will provide you constant, easy targets for your armies. If there are no enemy armies nearby, you should almost always attack an undefended city. Even if you only have a few units, your soldiers will have an advantage over the garrison guarding the city. Attacking and sieging cities is a much more effective way for dealing with opposing nations instead of meeting their armies on the field.  If the city is defended by nearby, besiege the city with a large army. Use other troops to engage the nearby armies, or let them attack your besieging army. In either case, you will have the advantage over the enemy, and will split their forces. When attacking a city, make sure you have the force necessary to take it and use the Auto-Resolve option. The computer will give you a higher advantage than normal. If the enemy comes out of the city to attack your siegers, play the battle manually. If any enemy attacks one of your cities, play the battle manually as well.

What is a summary?
Take out minor nations first. Attack undefended cities.