go on the offensive
US /ɡoʊ ɑn ðɪ əˈfensɪv/
UK /ɡoʊ ɑn ðɪ əˈfensɪv/

1.
攻勢に出る, 攻撃に転じる
to start to attack or to act in a way that shows you are ready to attack
:
•
After a period of defense, the team decided to go on the offensive.
守備の期間の後、チームは攻勢に出ることを決めた。
•
The politician decided to go on the offensive against his opponent's claims.
その政治家は、対立候補の主張に対して攻勢に出ることを決めた。