This is the essence of the game: the AI starts out with literally over 20,000 ships, you start out with something like 6. They don't give a flip about you. But as you start taking over their territory more, etc, they start to care more. However, it's basically a big bureaucracy, and not all of the AI ships are aware that you even exist, or what is going on. So there might be huge armies over near your planets, but that just makes those planets harder to take, it doesn't really increase your risk particularly. In general, adjacency to huge planets does not matter, because AI ships are not allowed to attack unless you set them free or there is a cross-planet attack.
There are three main rulesets for AI Ships:
- Free (can do anything, and attack you whenever)
- Guard (can do anything within their guard radius, but that is it)
- Special Forces (move on patrol between planets, become Free when they see you).
How do ships become free?
- When ships come in via a wave, they are Free from the start.
- When you destroy a Guard Post, its ships become free.
- When you destroy a command station, there is a 50% chance of their ships becoming free.
- When the AI launches cross-planet attacks, it will set something like 1000 to 2000 ships free across its empire, really diffusely, so that the ships come at you from all directions.
- When Special Forces ships encounter your ships on a planet, they become Free.
- In the expansion, certain ships like Raid Engines and Alarm Posts can create extra waves or set ships free under different rules.
Otherwise, guards just guard, and special forces ships just patrol. This is the handicap of the AI, as it were, and what keeps it from slaughtering you in the first 30 seconds or less of the game. You're expanding through their space, and for the most part they are not actively hunting you. We as the humans have already lost the war, and are insignificant ants now. They still try to swat the ants, but it is not a huge priority for them compared to whatever other activities (that are largely unknown at the moment) they are doing. Their attention is basically focused outside the galaxy on something else. But, as you make ingresses into their territory, and cause increasing amounts of trouble for them, their estimation of you grows. They start seeing you as being more than an ant, and that causes much more challenges.
Hope that helps!