intervene
v.v. to get involved in a difficult situation to change what is happening or to prevent something bad. You usually do this to help solve a problem between other people or groups.
v. to come between disputing people or groups to mediate or modify a situation. Often implies an intentional action taken to prevent a negative outcome or to influence a process that has already begun.
The teacher had to intervene when the students started arguing.
The central bank decided to intervene in the currency market to prevent the local money from losing too much value.
While the government is often reluctant to interfere with private contracts, it will intervene if the terms are found to be predatory or if they violate fundamental human rights.
Back-formation from intervention, and/or from Latin interveniō (“come between”, verb).
The verb is intransitive and is almost always followed by the preposition 'in'.
The police intervened the fight.The police intervened in the fight.Intervene is intransitive; you must use 'in' before the situation or event you are entering.