Hitherto he had not attempted to occupy the hills on either side, but after the arrival of the new generals it was decided to include them within the lines. On June 13 the insurgents heard that the British were about to occupy Dorchester heights. They determined to frustrate this move by occupying the ridge stretching along the Charlestown peninsula, and called by the general name of Bunker hill. Accordingly on the evening of the 16th a detachment of 1,200 men, with six field-pieces, was sent from Cambridge for that purpose. When they arrived at the summit their leaders determined to advance farther and to fortify a lower eminence of the ridge nearer Boston, which was distinguished by the name of Breeds hill. There during the night they formed a redoubt and breastwork. At daybreak on the 17th they were discovered from the sloop _Lively_, and her guns roused the British army. Before long a battery in Boston and the guns of other ships opened fire, but did little mischief. The insurgents received a small reinforcement, and formed a line of defence, protected by a low wall and rail, from their redoubt northward to the Mystic, in order to secure themselves from a flank attack. If Gage had placed a floating battery on the Mystic, which would have taken them on the left flank, and had landed troops to the rear of the redoubt, held the neck, and so cut them off from their main body, he would have had them at his mercy. This would have been easy, for by taking up a more advanced position than was laid down in their orders, they left their rear exposed to attack. He decided, however, to storm their works. [Sidenote: _BATTLE OF BUNKER HILL._]