The three new commanders were dismayed by Gage's lack of activity and managed to rouse him to a limited offensive aimed at securing Boston by capturing high ground at Charlestown to the north and Dorchester to the south. News of the British plan reached the Americans, who decided on pre-emptive action. On the night of 16-17 June an American force some 1,200 strong under Colonel William Prescott moved onto Breed's Hill, rather than the slightly higher Bunker Hill.
At the same time Clinton was making a reconnaissance of the area prior to the planned British advance. On his return he advocated an immediate attack at dawn on the 17th, but Gage, believing that the American move was temporary turned down the idea. It soon became clear that the American move was serious. Clinton now suggests a two pronged British attack, taking advantage of their naval supremacy, with one force landing on the southern shore of the peninsula, roughly where the eventual attack was to take place, supported by a second landing behind the American position. Gage also turned down this idea, and instead decided on a single force of 2,200 men landing in front of the American positions and launching a frontal attack on the rebels.
Perhaps encouraged by the generally poor performance of colonial troops during the Seven Years War, the British generals were very damning of their American opponents - Burgoyne described them as an 'undisciplined rabble', who could be expected to crumble under attack by regular soldiers. The attack was commanded by General Howe, who had a reputation as an expert on amphibious and light infantry operations. On this occasion his skills must have deserted him. The British took two hours to deploy, and even then the artillery was badly deployed and had little or no impact on the battle.
When the first British attack finally came it was a disaster. The standard British tactic for attacking fortifications was to advance in columns, with sharpshooter between them to fire at the defenders then at the end rush the defences in line. Howe decided to advance in line instead. The British were allowed to get close to the American lines before being subjected to a devastating fire that shattered the first attack. The same fate was suffered by a second attack, although Howe had reverted to columns. It was only when the Americans began to run out of ammunition that the third British attack was able to breach their defences and engage in the bayonet fighting that Howe had been relying on. By this point the British troops were exhausted by their efforts, and this combined with a covering fire from American sharp-shooters to prevent a successful pursuit.
While the Americans had suffered heavy casualties, with 150 dead and 270 wounded, British losses had been far worse, with 226 killed and 828 wounded. The British in Boston were thoroughly demoralised by their victory. It became clear that they could not afford further actions against the American positions around Boston, giving the Americans effective freedom of movement, both around Boston and in the other colonies, where British control was rapidly lost. Gage and then Howe persistently overestimated the strength of the American forces surrounding them, seeing at least 10,000 men at all times, a figure that would have surprised Washington, who was well aware of the weakness of his force over the winter of 1775. The American stand at Bunker Hill played a major role in convincing the British of the weakness of their position. In September Gage was ordered to move from Boston to a port better suited to the navy, but it not until the following March that his army, now commanded by Howe, made a move. Bunker Hill had effectively kept the main British army in North American inactive for nearly a year.