This is the 2173rd most frequent Russian word.
военном
The word "военном" is the prepositional case of "военный" and means "military" or "related to war" in English.
The word 'военном' is used here as an adjective in the prepositional case to describe 'гарнизоне' (garrison), indicating its military nature.
Мой дедушка служил в военном гарнизоне.
My grandfather served in a military garrison.
The word 'военном' again functions as an adjective in prepositional case, modifying 'совете' (council) to specify its context as related to the military.
На военном совете решались важные вопросы.
Important decisions were made at the military council.
Here, 'военном' is an adjective in the prepositional case modifying 'конфликте' (conflict) to describe its military context.