Stop fortress instant building

A player who buys fortresses right before you attack him, cannot be defeated.

Because you cannot attack him in any city.

And you lose a substantial number of your units if he catches them with an instant 4-5 level fortress.

In short, because some players buy fortresses before attacks, they make their map unplayable.

It is happening again to me as I type this.  Normal speed.  9 game days in 9 real life days.  All that work is wiped out because a player is buying the win by forbidding me to attack him in cities.

If you stop players from instantly buying fortresses, then the rest of us won’t quit your maps when it happens.

The fact I am level 19 means nothing when I am not allowed to attack cities, only units between cities.

Yes you can plan to hit a level 5 fortress with stormtroopers, cannon, and planes if you can make them, but you cannot do that for every city you attack.  The map is unplayable at that point.