Here's a little story on the utility of forts for launching surprise attacks:
I'm currently playing a civ pitboss game where one of my supposed allies went and screwed me over. This is to be expected of course, but since we are a group of people who will regularly be playing pitboss games down the line, there's a certain degree of reputation to it - he is more than twice my size, has a big tech lead on me, and is generally in a position to be a big mean bully all that he wants.
In this situation, he promised to aid me in a struggle versus a common neighboor, but he never joined up, as he became otherwise engaged...he has since refused to sell me troops, or even upgrade my troops for profit, so he's clearly milking the fact that two of his neighboors are at war and wants to stretch it out for as long as possible.
I need to get back at him, ideally, since that'll send a clear message that you don't want to mess with me by playing diplomacy games, so I devised the following strategy.
Now bear in mind, we don't actually share a land border; he just has a bit of culture on my land, since he controls the delta of water between he and I. Here's a rough sketch of the geography:
Ally | quarry|
____|______|
water|Me |
water| |
His tech: Cannons and Riflemen
My quarry's tech: very recent musketmen, heading towards riflemen
My tech: samurai and crossbowmen and catapults.
- Build a fort, and fill it up with 8 samurai and 2 galleys. Promote the samurai with amphibious promotion. It must be within 3 squares of my "ally's" nearest coastal city.
- Make a deal with the game leader, who's currently at war with my ally. The game leader has infantry and panzers. I give him my nearest city, but ensure that it's empty, and I gift him my samurai and galleys. I make some kind of bargain where he gets some cash if he promptly upgrades the samurai and galleys, loads the infantry into the galleons, and give me my city back.
- I make sure to name the units in such a fashion that my ally knows who screwed him over.
Since my ally's flank is completely and utterly exposed, and since he's not even the main target in the war with the game leader, it should allow for a surprise attack he won't see coming.