Here's what I found and checked in the game :
If you precharge a Settler, it can build an instant-fort right next to the city.
So, in other words, if you need to build a fortress next to the enemy city and you need to do it very quickly (ideally within one turn), give your settler an order to build a fort somewhere in a safe area. One turn before the fort is ready move the settler to the square where you actually want to build a fort, e.g. next to the enemy city and give an order to build a fort. The fort will be ready next turn giving yor opponent not much time to react.
The only thing I found tricky is that the time required to have a fort completed tends to vary. It is the same for all types of terrain but somehow depends on which turn (year) you gave an order to build a fortress. Most of the time it takes 5 turns, but for some of the orders (during my testing at Prince level) it took much longer - up to 26 turns. For my tests I used 10 settlers on different terrains and they all completed their job at the same time but the time itself i.e. number of turns varied significantly
and I couldn't find any regularity or consistent pattern in those changes.
I would appreciate if someone would clarify on this.
If you precharge a Settler, it can build an instant-fort right next to the city.
So, in other words, if you need to build a fortress next to the enemy city and you need to do it very quickly (ideally within one turn), give your settler an order to build a fort somewhere in a safe area. One turn before the fort is ready move the settler to the square where you actually want to build a fort, e.g. next to the enemy city and give an order to build a fort. The fort will be ready next turn giving yor opponent not much time to react.
The only thing I found tricky is that the time required to have a fort completed tends to vary. It is the same for all types of terrain but somehow depends on which turn (year) you gave an order to build a fortress. Most of the time it takes 5 turns, but for some of the orders (during my testing at Prince level) it took much longer - up to 26 turns. For my tests I used 10 settlers on different terrains and they all completed their job at the same time but the time itself i.e. number of turns varied significantly
and I couldn't find any regularity or consistent pattern in those changes.
I would appreciate if someone would clarify on this.
