Why did the united states become involved in nicaragua in the 1980s?

All through Nicaraguan history, the US has been engaged with Nicaragua legislative issues, financial aspects, and military, some of which I picked up amid my trek to Nicaragua. In the year 1850, the US and Great Brittan marked a bargain that let the two nations approach a between maritime exchange through Nicaragua without Nicaragua's assent 29 years after it picked up freedom from Spain.