Tried restarting this quest many times but to no avail. Wanted to complete special mission for the cossacks and the village leader doesn't recognise the password even if it is the correct one. Also when you ask the guy who gives you the special mission what the password is, he says: with fire and sword but its in polish not english.
This has led me to believe its a text recognition issue, since the village leader says the 'with fire and sword' password is incorrect.