noun which may take the genitive case particle 'no'
defensive-only; constantly on the defensive
Describes a situation where one side is forced to defend without any chance to attack. Often used in sports, debates, or military contexts.
試合は防戦一方で、相手に攻め込まれ続けた。
The match was defensive-only, and we were constantly attacked by the opponent.
議論では防戦一方になり、反論する余裕がなかった。
In the debate, I was constantly on the defensive and had no room to counterargue.
攻め一方 means 'offensive-only' or 'constantly on the attack', the opposite of 防戦一方.
Compound of 防戦 (defensive battle) and 一方 (one direction, only). The exact historical derivation is uncertain, but the meaning is transparent from its components.