AI War - Prerequisites to Winning
What do you need to do to win a game of AI War?
Simply put, the only objective of AI War is to kill the AI Homeworld Command stations without losing your own Homeworld Command Stations. This is a bit trickier on Multiplayer since as long as one of the human players hasn't lost any of their home command stations, the alliance can still win.
Core Shield Generators
Core Shield Generators are an addition to the base game that are on by default. Their activation can be controlled via the Ships tab during map generation.
Their primary purpose is insuring that players capture a minimum number of planets before attempting to take a homeworld. Because the A generators are always located on planets with Advanced Reseach Stations and B generators are located on planets with Advanced Factories, it helps orient players toward capturing strategic assets. These assets dramatically improve the chances of success against the AI homeworlds. You'll rarely find them prohibitive unless you're playing a very non-standard set of tactics, which is based around a very minimal AIP value.
When activated, you will always end up destroying a minimum of 8 of these structures on each playthrough. To destroy one, you must have a player command station building on the planet.
You can find out more details about the automated placement in the section on this page: AI War - End Game
Right, but what do you NEED to win?
This is a different question, and like many other questions in sandbox style games: "It Depends."
In general, you will require a very strong fleet to be able to overcome the high-level (Mark V) defenders at the AI Homeworlds, and also destroy their guardposts. You will need to destroy all the guardposts on the homeworld before you can damage the AI Homeworld Command Station. This can be daunting. After that you'll need to assault the AI Command Station, almost always defended by two high mark forcefields, a Fortress III, and a small mass of Mark V ships that will hide under the forcefields and attack your assault force.
You will also want to take control of enough positions to be able to attack without causing deepstrike threat. Deepstrike happens whenever you're attacking more than 4 systems away from a neutral or friendly planet. Deepstrike causes a continuous spawning of zombie ships (much like an AI Eye) from the two AI Homeworld Exo-gates.
Once you've done that once, you'll need to do it again on the OTHER AI Homeworld. Both AIs (like two players in Multiplayer) will continue to function as normal as long as one of those homeworld command stations exist. Once both are destroyed, you'll win that game.