This is the 5654th most frequent Polish word.
wojennej
"Of war" or "war-related."
'wojennej' here describes 'klęski' to specify its nature as related to war.
Historia tej wojennej klęski była omawiana na lekcji.
The history of this wartime defeat was discussed during the lesson.
'wojennej' here acts as an adjective characterizing 'kampanii' as pertaining to war.
Żołnierze opowiadali o trudach wojennej kampanii.
The soldiers talked about the hardships of the wartime campaign.
'wojennej' here modifies 'przeszłości', indicating it is related to the time of war.