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Firstly, starting heroes (at 200%) rarely manage to kill anyone, and they don't need an army; it's better to quickly acquire the essentials (lumber mill, quarry, resources).
Secondly, the main hero travels with warriors from their own Fortress, not with the fastest units! Their own units don't suffer a penalty when moving through swamps. That's why I suggest keeping only Fortress warriors for starting heroes!
But defense is still a plus.
Not for everyone. Tactics are rarely learned for mages of any Fortress (except for the Citadel).
Magic is generally weak for Swamp players. Hence the conclusion: focus on warriors.
Slowness is very unpleasant, as is any magic. The Fortress is weak against magic, I agree, but that's not a reason to give up! You can always find a way.
Well, it depends on the number of dragonflies (and, of course, the enemy army) and the level of defense. They can hold off the archers until the army arrives, and the Fortress has a very good army:
Hydras are excellent fodder, attacking multiple targets.
Gorgons deal very good damage to high-level warriors thanks to their deadly gaze.
Basilisks can turn enemies to stone.
And wyverns are usually taken in large numbers (on random maps, there are often snake nests). Besides, it's quite easy to place wyverns at the beginning of the game.
You probably haven't encountered an opponent who knows how to play Fortress well.
In the Fortress, besides what you can't learn, you also won't be able to reach places quickly. :)
And wyverns don't cause difficulties???
It's difficult to capture, but possible. Building up magic takes a long time, but there's nothing you can do about it. This is the Fortress's weakness: magic.
It's difficult to capture, but possible. Building up magic takes a long time, but there's nothing you can do about it. This is the Fortress's weakness: magic.---Exactly, it's MAGIC, which is very important in the game, especially (city portal and teleportation). If the first one can still be learned by Swamp players (although again, the probability is much lower than for other Fortresses), then dreaming of a good 4-turn teleportation is all you can do... and without it, it will be very difficult to play on large maps, especially against human players.