noun
intervention
in-ter-VEN-shun/ˌɪntərˈvenʃn/
Action taken to change a situation by becoming involved in it.
His intervention separates the two men before their argument becomes a fight.

Etymology
An intervention is literally a “coming between.” That image extends from interposing oneself or interceding for someone to taking action that interrupts or changes a situation.
In context
Let us turn to Afghanistan. 10 years after that military intervention, that country is far from secure.
More examples
- The early intervention helped the child catch up at school.
- They requested government intervention in the dispute.
- The mediator's intervention brought both sides back to the table.
Forms
intervention · interventions
intervene verb — become involved to affect a situation
Similar words
- involvement
- Does not necessarily imply an action intended to change events.
- interference
- Usually suggests unwelcome involvement rather than neutral or helpful action.