Verb
take the offensive (third-person singular simple present takes the offensive, present participle taking the offensive, simple past took the offensive, past participle taken the offensive)
(idiomatic) To attack instead of defending; to be bold and proactive.
In 1149, Manuel recovered Corfu and prepared to take the offensive against the Normans, while Roger II sent George of Antioch with a fleet of 40 ships to pillage Constantinople's suburbs. Source: Internet
With the Americans in retreat Howe was then able to take the offensive and on November 16, landed his troops on the island and surrounded and captured Fort Washington, resulting in high Continental casualties. Source: Internet