On June 13 , 1775 , the leaders of the colonial forces besieging Boston learned that the British were planning to send troops out from the city to fortify the unoccupied hills surrounding the city , giving them control of Boston Harbour .
On June 13 , 1775 , the leaders of the colonial forces besieging Boston learned that the British generals were planning to send troops out from the city to occupy the unoccupied hills around the city .