Reference to map, “Boston and vicinity,” already used in the January number of this Magazine to illustrate the siege of Boston, will give a clear impression of the local surroundings, at the time of the American occupation of Charlestown Heights. The value of that position was to be tested. The Americans had previously burned the lighthouses of the harbor. The islands of the bay were already miniature fields of conflict; and every effort of the garrison to use boats, and thereby secure the needed supplies of beef, flour, or fuel, only developed a counter system of boat operations, which neutralized the former and gradually limited the garrison to the range of its guns. This close grasp of the land approaches to Boston, so persistently maintained, stimulated the Americans to catch a tighter hold, and force the garrison to escape by sea. The capture of that garrison would have placed unwieldy prisoners in their hands and have made outside operations impossible, as well as any practical disposition of the prisoners themselves, in treatment with Great Britain. Expulsion was the purpose of the rallying people.
General Gage fortified Boston Neck as early as 1774, and the First Continental Congress had promptly assured Massachusetts of its sympathy with her solemn protest against that act. It was also the intention of General Gage to fortify Dorchester Heights. Early in April, a British council of war, in which Clinton, Burgoyne, and Percy took part, unanimously advised the immediate occupation of Dorchester, as both indispensable to the protection of the shipping, and as assurance of access to the country for indispensable supplies.
General Howe already appreciated the mistake of General Gage, in his expedition to Concord, but still cherished such hope of an accommodation of the issue with the Colonies that he postponed action until a peaceable occupation of Dorchester Heights became impossible, and the growing earthworks of the besiegers already commanded Boston Neck.
General Gage had also advised, and wisely, the occupation of Charlestown Heights, as both necessary and feasible, without risk to Boston itself. He went so far as to announce that, in case of overt acts of hostility to such occupation, by the citizens of Charlestown, he would burn the town.
It was clearly sound military policy for the British to occupy both Dorchester and Charlestown Heights, at the first attempt of the Americans to invest the city.
As early as the middle of May, the Massachusetts Committee of Safety, as well as the council, had resolved “to occupy Bunker Hill as soon as artillery and powder could be adequately furnished for the purpose,” and a committee was appointed to examine and report respecting the merits of Dorchester Heights, as a strategic restraint upon the garrison of Boston.
On the fifteenth of June, upon reliable information that the British had definitely resolved to seize both Heights, and had designated the eighteenth of June for the occupation of Charlestown, the same Committee of Safety voted “to take immediate possession of Bunker Bill.”