General Israel Putnam (who left his plow to defend his country) was in charge of the patriots, assisted by very capable officers including Colonel William Prescott. At the time of Bunker Hill (June 17, 1775), the Americans did not have a navy, but British naval ships were in Boston Harbor - very near to Charlestown.

The Colonials (about one-third were African-Americans) were dug in along the high ground of Breed's Hill. Fighting with notoriously inaccurate muskets that were slow to load and produced lots of smoke,  (you will need a Windows Media Player for this National Park Service MPEG movie), the patriots were low on ammunition. Implementing orders from General Putnam, Colonel Prescott issued one of the most famous (and perhaps legendary) orders of the American Revolution:

When the Redcoats, who marched up the hill in formation, were about 15 paces away, the patriots fired, halting the British advance. The Brits stormed Breed's Hill a second time. Again, the patriots forced a retreat. By the third British advance (look at the bottom of this link for details of the three attacks), the patriots were out of ammunition. Using their bayonets and throwing stones, the Americans could not hold Breed's Hill. The victory cost Britain more than 1,000 casualties - about half their force. Four hundred patriots died, including General Joseph Warren.

Victorious, (follow this link to a terrific U.S. Military Academy annotated map of the battle and its aftermath), the Redcoats began a siege of Boston. America, meanwhile, appointed (this link is the original commission) a reluctant Commander-in-Chief: George Washington, a farmer/surveyor from Virginia, married to Martha Custis, and a hero of the French and Indian War.