In the face of the Marsh army, who had members like the giant multi-headed serpents that wielded catastrophic military power, even the sturdiest fortress would become nothing more than an ordinary small village.
The reason why the Red Tree fortress could sustain up till the now was because it had one out of the four Legendary Masters and a demigod holding the fort.
Putting aside the discussion of the four Legendary Masters for the moment, just that demigod alone was a through-and-through strategic martial force in his own right. With him around, even an army of thousands of men and horses would not stand a chance of victory.
However, the Marsh army also had Demigod Masters.
For ages, the Marsh races had been able to resist the invasion of the humans. And they mainly depended on those Demigod Masters who lingered in the human world and refused to leave.
