This is the 611th most frequent Japanese word.
軍事
Military affairs.
In this sentence, "軍事" (military) is used as a noun to attribute expertise areas, directly relating to strategies and operations involved in defense and warfare scenarios.
彼は軍事戦略の専門家です。
He is an expert in military strategy.
Here, "軍事" refers to military power or forces collectively, often used in the context of state-level defense policies and capabilities.
その国は軍事力を強化し始めました。
That country has started strengthening its military power.
In this instance, "軍事的" is the adjective form of "軍事", describing actions as military-related, highlighting its use in modifying nouns to provide context.