“Secure some advantageous Posts near Boston”

On 13 June 1775, the New Hampshire Committee of Safety, meeting in Exeter, sent this message to the Massachusetts Committee of Safety in Cambridge:

Gent’n—

By a Gent’n of undoubted veracity (who left Boston last Friday & who had frequent oppor’s of conversing with ye principle officers in Gen’l [Thomas] Gage’s army) we are informed that there is a great probability that when the expected reinforcement arrives from Europe that Gen’l Gage will secure some advantageous Posts near Boston, viz. Dorchester & Charlestown. We are unacquainted with the importance of those posts, but if this hint sho’d be in any degree usefull it will give us pleasure.

That is often taken as the spur that led the Massachusetts committee to order troops into Charlestown ahead of the British, bringing on the Battle of Bunker Hill. But it was probably one of many indications that the British, now reinforced with three more generals and many more soldiers, were about to make an aggressive move.

Furthermore, the Massachusetts leaders already knew about the strategic importance of the Dorchester and Charlestown peninsulas. They had been hearing warnings that the Gage and his officers wanted those posts for over a month. Most of the inhabitants of Charlestown had evacuated, fearing a fight. (The Dorchester peninsula was less populated to begin with.)

The main question was when the British might move. On some occasions, such as the march on Salem in February, the army had acted on a Sunday, when so many New Englanders were in church. The next Sunday was 18 June.