all-out war; full-scale war
Refers to a war involving extensive forces, resources, and territory, as opposed to a limited or local conflict.
The country strengthened its military in preparation for a full-scale war.
Historians point out that the conflict had the potential to escalate into an all-out war.
全面戦争 also means 'all-out war' but emphasizes the involvement of all fronts and aspects of society, while 大規模戦争 focuses on the scale and magnitude.
局地戦 is a 'local war' or 'limited war', the opposite of 大規模戦争.
Compound of 大規模 (large-scale) and 戦争 (war).