The British Make Mistakes

In the year of 1775, British did not take the Patriots as serious enemies, they knew very well the size of their empire, and the differences they had with Patriots.
in this year, a new commander, Lord William Howe ordered a frontal assault in the middle of the day in order for them to take the hill.
The British underestimated the Patriots, and did not think of them as enemies but as living proof of how powerful they could be. 
Patriots, in the other hand had a psychological victory, because they felt they had defeated the British. But truth was, British had won the war only because of the lack of ammunitions from the Patriots.

On January, 1776 there occurs a change of colonel, Henry K. arrives with reinforcement for the Patriots who were outside Boston. They pushed canons from New York to Boston, and on March of the same year, they get Boston back.