Can someone explain the strategic reserve to me? Specifically, when is the AI allowed to draw from it?
The Strategic Reserve is a large pool of points that each AI has, that can be used to spawn a group of Mk V ships. These ships will defend the system they spawn in, but will not leave. If all human forces depart/die, the Reserve units will un-deploy (turning back into abstract points). Points accumulate as time passes (rate and cap are based on difficulty and AIP), and destroying Reserve ships lowers the current total. Only the AI that owns a system will deploy the Strategic Reserve to that system.
The Reserve can be deployed as long as there is an AI command station present, and only is systems where a specific condition is met.
The Reserve will deploy for:
The SuperTerminal - will deploy enough units to bring the Reserve down to 90% of max. This means up to 10%.
Core Worlds - Down to 70% of max.
AI Homeworlds - The entire thing.
Additionally, Cross Planet Attacks will draw a portion of their strength from the Strategic Reserve, in addition to using ships already present in the galaxy. In this case, the units spawned will be at the current AI tech level.
The "Reservist" AI type has a larger Strategic Reserve than other AI types (a x3 higher point cap), PLUS the Reservist AI will deploy the reserve more often. It will deploy up to 10% (down to 90% remaining) for systems with Advanced Factories, Advanced Starship Constructors, and Core Shield Generators. I don't think it will deploy the Reserve for systems with Fabricators, but someone should double-check me on that.