This is the 385th most frequent Russian word.
войне
The word "войне" is the dative or prepositional case form of "война," which means "war" in English.
The word 'войне' is used in the prepositional case to denote the topic of the conversation or written work.
Мы читали книгу о войне.
We read a book about the war.
The word 'войне' is used in the instrumental case to indicate the time frame in correlation to the main event mentioned.
После войны страна восстановилась.
After the war, the country recovered.
The word 'войне' here is in the prepositional case to indicate spatial or situational context.