Anyone use forts to slow down marauders?

[slebrun]

and if the french fortified the belgian border as well?

The same thing, really. Hitler had the advantage, in that he was fighting a 20th century war, with 20th century equipment, using 20th century tactics, against opponents still thinking in the 19th century.

The Blitzkreig, for example, was well designed to exploit the 'wide but shallow line of defense' that characterized WW1.

But you'll also notice that very quickly, the Wehrmacht started having to work for it's lunch. The Blitzkreig was a frightening thing when it happened to people still thinking 'trenches,' which was itself simply a modification of 'line the redcoats up and start volleying.' But as soon as you start thinking about it, you start coming up with ways to counter, and tricks for tanks of your own.

Also, the tactics were specifically designed to attack west. You can see this when Germany (rather stupidly) decided to attack Russia; it's hard to have a 'lightning war' when your tanks are all bogged down in the mud of the Rasputitsa, or are stuck in the howling snow storms of a good Russian winter.

[johnmcd]

Anyway, I think it already pays enough to be the defender. It's very easy to hole up in your cities and sit out the invasion but lose your fields. If it became so that you didn't even lose your fields when you defended waging war would become even less of a tactic.

[marvinkosh]

In the early game, before forts are available, I will put archers on hills or in forest where I'm likely to be attacked by barbies. Nailing them before they get near my cities is well worth what the archers may cost. Plus, in repelling these attacks, my units get blooded a bit more than they would if they sat in the city waiting for an attack.

When forts become available, they make it possible to dig your claws into land which usually doesn't grant any defensive advantage. Often the position of a fortification determines its overall effectiveness. Having a medic stationed inside can make a big difference to your ability to get units ready for battle again.... which is useful when those barbie axemen seem to come in rippling waves

[xenophile58]

Well, I haven't used forts myself. If you've built a strong enough military to defeat the invasion. I don't see their point. If you don't then hunkering up in the cities building one seems the best course. Isolated forts can only channel an invasion, not stop or slow one.
In fact, I think that's about right, both in game terms and historically. The whole point of military tactics is to pit strong forces against weak ones (At the extreme, soldiers against civilians - as exemplified say by Sherman's Georgia campaign). Fortresses permit a smaller garrison to shelter from a force they can't defeat, but by continuing to exist constrain the attacker from dispersing - in case of sallies or being attacked by a combination of forces including the fortress garrison. In Civ 4, the cultural bog the attackers are in slows their movement anyway, while a mobile defence sheltering in a fort can attack any lone pillager and still retreat into the fort.
Forts were normally built to protect the garrison for an area, more rarely to control natural chokepoints. Only the latter might require an invader to attack, but I think that the usual point of a fort is rarely the fort - it's the strength of the garrison it shelters.