[Idea] out-of-turn intercept

Currently with the way things are, it's very hard to defend caravans or to spot invading troops since the game doesn't track movements of enemies through your territory.

A nice feature would be to allow my army to patrol/guard. When in this state, they don't move , but can initiate combat out of turn with a hostile army that comes within its reach. We could put limits on reach such as only as far as 1/2 their total movement with a minimum of 1 and a maximum being their site radius (Can't intercept what you can't see). They should only be able to intercept once and use up all their movement for the next round after intercepting an army.