This is the 363rd most frequent Russian word.
войну
The Russian word "войну" means "war" (accusative case).
Here, 'войну' is in the accusative case singular, serving as the direct object of the verb 'выиграл' (won).
Он выиграл войну благодаря великому стратегическому уму.
He won the war thanks to his great strategic mind.
In this sentence, 'войну' is also in the accusative case singular, acting as the direct object of the verb 'описывал' (described).
Писатель подробно описывал войну в своем романе.
The writer described the war in detail in his novel.
Here, 'войну' serves as the object of the verb 'пережили' (experienced), once again demonstrating its role in the accusative case singular as the direct object.