This is the 614th most frequent Russian word.
боевые
"Боевые" translates to "combat" or "military" in English.
In this sentence, 'боевых' is used attributively to denote the type of actions, which are related to military combat.
Они участвовали в боевых действиях на передовой.
They participated in combat actions on the front line.
Here, 'боевые' conveys the aspect of being warlike or combat-related in the context of structured practices and skills.
Боевые искусства требуют дисциплины и упорства.
Martial arts require discipline and perseverance.
Here, 'боевых' is an adjective describing the nature of the operations as related to combat situations.