Even as George Washington prepared to take command of the Continental Army, the war around Boston was already intensifying.
Following Lexington and Concord, thousands of colonial militia members had surrounded the city, trapping British forces inside Boston while both sides prepared for further fighting. British commanders hoped to break the growing siege and regain control of the surrounding countryside before colonial resistance became more organized.
The area around Boston contained several important hills overlooking the city and harbor.
Among them were Breed's Hill and nearby Bunker Hill on the Charlestown Peninsula north of Boston. Whoever controlled these heights possessed a major strategic advantage, particularly for artillery placement overlooking British positions and shipping.
In June 1775, colonial leaders learned that British forces planned to seize the hills.
To prevent this, militia units moved onto the peninsula during the night of June 16 and quickly began constructing defensive earthworks on Breed's Hill. Working in darkness with shovels and picks, the colonists built trenches and fortifications while British warships and troops remained nearby.
When British commanders awoke the next morning, they were stunned by what they saw.
Colonial forces had established fortified positions within striking distance of Boston itself. British leaders concluded the defenses had to be destroyed immediately before they became even stronger.
General William Howe prepared a direct assault.
On June 17, 1775, British troops crossed Boston Harbor and advanced toward the colonial fortifications under intense summer heat. The British soldiers were highly trained professional troops, experienced in battlefield discipline and conventional European warfare. Many British officers expected the inexperienced colonial militia to break quickly once attacked.
But the colonists held their ground.
As British forces climbed the hill in organized formations, colonial defenders waited behind earthworks and fences for the enemy to move within close range. According to tradition, American officers ordered their men not to fire until they could clearly see the whites of the British soldiers' eyes — though the exact wording and origin of the command remain uncertain.
When the colonists finally opened fire, the results were devastating.
British lines suffered heavy casualties as disciplined volleys tore through advancing troops. The attack faltered, regrouped, and advanced again under intense gunfire. Once more, the colonists inflicted severe losses.
Still, the British continued pressing forward.
The colonial defenders faced a critical problem: ammunition shortages. As supplies ran low, maintaining resistance became increasingly difficult. During a third British assault, many American defenders could no longer sustain effective fire.
British troops finally breached the colonial positions.
The fighting became chaotic as colonists retreated from the hill, some engaging in desperate hand-to-hand combat before withdrawing. The British technically won the battle by capturing the ground, but the cost was shocking.
More than one thousand British soldiers were killed or wounded.
Among the casualties were many officers, and British commanders were deeply disturbed by the severity of the losses. The battle demonstrated that colonial forces, even when poorly supplied and only partially trained, could stand against experienced British regulars in major combat.
Colonial losses were significantly smaller, though still painful.
Among the dead was Dr. Joseph Warren, an influential Patriot leader from Massachusetts whose death became a powerful symbol of sacrifice for the revolutionary cause.
The Battle of Bunker Hill carried enormous psychological importance.
For the British, the victory revealed that defeating the rebellion would likely require far more time, bloodshed, and resources than many leaders had expected. For the colonists, the battle proved they could fight effectively against Britain's professional army.
News of the battle spread quickly throughout the colonies and across the Atlantic.
Many Americans viewed the heavy British losses as evidence that the revolutionary cause could survive. At the same time, British officials increasingly recognized that the conflict was becoming a serious and dangerous war rather than a temporary disturbance.
The battle also hardened attitudes on both sides.
Violence was escalating, casualties were mounting, and hopes for quick reconciliation continued fading. The Revolution was becoming a long and costly struggle whose outcome remained far from certain.