William Prescott developed military experience in the Massachusetts provincial forces before becoming a Revolutionary officer. He served in the imperial wars of the mid-eighteenth century, including the campaign in Nova Scotia in 1755, then returned to farming and local affairs at Pepperell. Opposition to British measures in the 1770s drew him into organized resistance. He supported Boston after the closing of its port and led local militia toward the fighting that began in April 1775.

His best-known command came during the night of 16–17 June 1775. Prescott led troops onto the Charlestown peninsula, where they constructed a redoubt on Breed's Hill under the direction of the engineer Richard Gridley. The resulting engagement became known as the Battle of Bunker Hill. He commanded within the redoubt, encouraging men under bombardment and helping organize resistance to the British infantry assaults.

Responsibility on the battlefield was shared and sometimes disputed among officers, including Israel Putnam and other provincial commanders. Prescott should therefore not be presented as the uncontested commander of every American position. His men helped repel repeated attacks before shortages of ammunition and the final British advance forced a retreat. The British took the ground at heavy cost, while the fighting demonstrated that the provincial army could resist trained regulars in prepared positions.

Prescott continued in Continental service during the siege of Boston and the campaigns that followed, then returned to Massachusetts public life. He served in the state legislature and maintained his connection with the communities from which his soldiers had come. Later commemorations made him a symbol of determination at Bunker Hill, sometimes attaching sayings without contemporary evidence. His career is better grounded in provincial military experience, local resistance and his leadership at the redoubt than in a single disputed battlefield quotation.