skilled in battle; battlewise; experienced warrior
Describes a person who is adept at warfare or combat, often with a connotation of practical experience rather than just theoretical knowledge. Can be used as a noun or adjectival noun.
He is skilled in battle and has survived many fights.
That general is known for being battlewise.
Compound of 戦 (いくさ, 'battle') and 上手 (じょうず, 'skillful'). The reading いくさ is a native Japanese word for warfare, while じょうず is a common Sino-Japanese suffix meaning proficiency.