1
general::
Phrase(s): take the initiative (to do something)
to activate oneself to do something even if one has not been asked to do it. • The door hinges squeak because no one will take the initiative to oil them. • Sometimes, in order to get things done, you have to take the initiative.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Begin a task or plan of action, as in The boss was on vacation when they ran out of materials, so Julie took the initiative and ordered more. This term uses initiative in the sense of "the power to originate something," a usage dating from the late 1700s.
American Heritage Idioms