NEW YORK (AP) — As the U.S. marks the 250th anniversary of the Battle of Bunker Hill, it might take a moment — or more — to remember why.

Start with the very name.

“There’s something percussive about it: Battle of Bunker Hill,” says prize-winning historian Nathaniel Philbrick, whose “Bunker Hill: A City, A Siege, A Revolution” was published in 2013. “What actually happened probably gets hazy for people outside of the Boston area, but it’s part of our collective memory and imagination.”

“Few ‘ordinary’ Americans could tell you that Freeman’s Farm, or Germantown, or Guilford Court House were battles,” says Paul Lockhart, a professor of history at Wright University and author of a Bunker Hill book, “The Whites of Their Eyes,” which came out in 2011. “But they can say that Gettysburg,D-Day, and Bunker Hill were battles.”

Bunker Hill, Lockhart adds, “is the great American battle, if there is such a thing.”

Much of the world looks to the Battles of Lexington and Concord, fought in Massachusetts on April 19, 1775, as the start of the American Revolution. But Philbrick, Lockhart and others cite Bunker Hill and June 17 as the real beginning, the first time British and rebel forces faced off in sustained conflict over a specific piece of territory.

A day-long reenactment of the battle got underway Saturday morning with the seaside city of Gloucester standing in for Charlestown. Organizers chose a state park some 35 miles (56 kilometers) from Boston to stage the battle because such activity is prohibited at the actual site.

Hundreds of onlookers watched as sharpshooters positioned on a rocky outcropping fired upon red-coated British sailors landing in the harbor. During the actual battle, British soldiers responded by setting a fire to drive them off and used the smoke to mask their movements.

Bunker Hill was an early showcase for two long-running themes in American history — improvisation and how an inspired band of militias could hold their own against an army of professionals.

“It was a horrific bloodletting, and provided the British high command with proof that the Americans were going to be a lot more difficult to subdue than had been hoped,” says the Pulitzer Prize-winning historian Rick Atkinson, whose second volume of a planned trilogy on the Revolution, “The Fate of the Day,” was published in April.

The battle was born in part out of error; rebels were seeking to hold off a possible British attack by fortifying Bunker Hill, a 110-foot-high (34-meter-high) peak in Charlestown across the Charles River from British-occupied Boston. But for reasons still unclear, they instead armed a smaller and more vulnerable ridge known as Breed’s Hill, “within cannon shot of Boston,” Philbrick says. “The British felt they had no choice but to attack and seize the American fort.”

Abigail Adams, wife of future President John Adams, and son John Quincy Adams, also a future president, were among thousands in the Boston area who looked on from rooftops, steeples and trees as the two sides fought with primal rage. A British officer would write home about the “shocking carnage” left behind, a sight “that never will be erased out of my mind ’till the day of my death.”

The rebels were often undisciplined and disorganized and they were running out of gunpowder. The battle ended with them in retreat, but not before the British had lost more than 200 soldiers and sustained more than 1,000 casualties, compared to some 450 colonial casualties and the destruction of hundreds of homes, businesses and other buildings in Charlestown. Bunker Hill would become characteristic of so much of the Revolutionary War: a technical defeat that was a victory because the British needed to win decisively and the rebels needed only not to lose decisively.

“Nobody now entertains a doubt but that we are able to cope with the whole force of Great Britain, if we are but willing to exert ourselves,” Thomas Jefferson wrote to a friend in early July. “As our enemies have found we can reason like men, now let us show them we can fight like men also.”

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Rodrique Ngowi in Gloucester, Massachusetts, and Holly Ramer in Concord, N.H. contributed to this report.