This is the 1243rd most frequent Polish word.
wojną
"Wojną" means "war" (instrumental form) in English.
In this sentence, 'wojną' is used as a noun in the instrumental case (similar to 'about the war'), reflecting its role in discussing a specific conflict.
Długo rozmawialiśmy o wojną, która zniszczyła ten kraj.
We talked at length about the war that devastated this country.
Here, 'wojną' again appears in instrumental case, but it conveys an associative meaning, indicating involvement or thematic connection to the adventures.
Przygody wojną zakończyły się już dawno temu.
The adventures with the war ended long ago.
In this context, 'wojnę' is the accusative form of the noun, representing direct reference to the concept of war experienced by a generation.