What was Paul Revere trying to prevent the British from doing?

He was trying to give warning to the colonists and the militia so they would be prepared and fight off the British army's initial attack.

Explanation:

The Boston Patriots had been preparing for a British military action for some time, and learning of the, Revere and Dawes set off, taking separate routes in case one of them was captured.  Patriots in Charlestown waited for a signal from Boston informing them of the British troop movement because they previously agreed that one lantern would be hung in the steeple of Boston’s Old North Church if the British were marching out of the city by Boston Neck, and two if they were crossing the Charles River to Cambridge. Two lanterns were hung so the armed Patriots set out for Lexington and Concord.The men roused hundreds of Minutemen, who armed themselves and set out to oppose the British.

to plan an idea out before

the answer is a. monarch