I have read in Northern Crusades [1] that in XII/XIII century forrests separating Prussia from Lithuania/Mazovia had been truly impassable (except for raiding p

I have read in Northern Crusades [1] that in XII/XIII century forrests separating Prussia from Lithuania/Mazovia had been truly impassable (except for raiding parties - raizes) and the only campaining had been possible along large rivers. Lituanians had it easier because they had been bringing siedge equipment and canons downstream. So there is some change although meassured in centuries :) [1] https://www.amazon.com/Northern-Crusades-Second-Eric-Christiansen/dp/0140266534 https://www.amazon.com/Northern-Crusades-Second-Eric-Christi...