It was 11 a.m. on Oct. 12, 1758, when the French approached the Post at Loyalhanna that the British were still building in the wilderness.

The attack came suddenly and unexpectedly, first on the men who were outside cutting vegetation surrounding the garrison, then on the nearby guards who also were startled and beaten to the ground.

The French unsuccessfully attempted to circle and take over the fort in a battle that lasted four hours through rain and heavy gunfire.

The British artillery drove back the French, who waited until nightfall for another strike. Again, they were defeated by the mortar fire from within the fort.

It was a turning point in frontier history.

This weekend, 250 years later, the site of that post -- later called Fort Ligonier -- will be invaded again.

Planners of the 250th anniversary of Ligonier Borough are expecting an estimated 200,000 people to descend on the 1-square-mile borough, population 695, in commemoration of the historic battle.

The annual Fort Ligonier Days celebration will be tomorrow, Saturday and Sunday.

"Fort Ligonier Days is always a source of pride for the locals, and this year it's more so because of the 250-year anniversary," said Annie Urban, director of marketing and development at Fort Ligonier Museum.

"It is always an exciting weekend full of events for the community and the visitors as well."

There is little doubt that the battle was significant. It led to the creation of Pittsburgh.

The presence of British and American troops at the fort in Ligonier caused the French to abandon Fort Duquesne at the confluence of the Allegheny, Monongahela and Ohio rivers, thus surrendering the Ohio Valley during the French and Indian War.

"Fort Ligonier provided a base camp and staging area for Gen. John Forbes' army to take Fort Duquesne," said Martin West, executive director of Fort Ligonier Museum. "That's the real importance of Fort Ligonier."

Many key people were there in that period, including George Washington, the future first president of the United States.

"This was really an important time for Washington, too," Mr. West said. "He gained his experience as a soldier and Fort Ligonier added to that. When he was with Forbes' army, he saw the largest army he would see until 1775. This helped him learn how to be an effective officer."

During the battle between 1,500 British and American troops and 590 French, there were 66 British casualties and far fewer among the French and their Indian allies.

"They were very good at this type of warfare in the woods," Mr. West explained.

The battle will be re-enacted at 2 and 4 p.m. on Saturday and Sunday. Between bellows of cannons, there will be demonstrations of drills and military tactics. There also will be displays of civilian life and Native American culture.

Local re-enactment units will be joined by units from as far away as Canada and New Hampshire.

"Their uniforms, equipment and weapons are accurate," Mr. West said about the re-enactors. "Some that will be here have been coming since the 1970s."

Although the fort and battles are mainstays of the popular weekend celebration, the whole town will be teeming with the excitement of other activities and attractions.

The event is widely known for its assortment of food booths manned by local nonprofit organizations. There will be more than 150 crafters and artists set up throughout town, selling art, clothes, crafts and other handmade wares.

Free outdoor entertainment will include bagpipers and drummers, concerts and other musical performances.

Visitors also can tour Fort Ligonier Museum. It has an impressive collection of original artifacts and a new world-class exhibit called "The World Ablaze: An Introduction to the Seven Years' War," which tells the story of that fascinating period of history.

"There is so much here," Mr. West said. "It is an astonishing thing that world-class museums exist in Western Pennsylvania. They are getting known more all the time and it's wonderful to have so many people attend the event to enjoy our history."

Thousands will line up to watch what may be one of the biggest parades in the region. This year's parade will begin at 11 a.m. Saturday and feature 400 members of the highly acclaimed Penn State Band.

The Quantico Marines, a traditional favorite military band, will create an excitement with their music and sharp uniforms. There will be 15 high school bands as well, including the well-regarded ones from Greater Latrobe and Franklin Regional.

The Old Guard, the only Army band to perform in genuine Revolutionary War uniforms, will add even more to the celebrated history. This band has performed for notable events at the White House and at the Olympics, the Indianapolis 500 and the Super Bowl.

There will be many more units, including 2,000-pound Budweiser Clydesdales pulling their company's beer wagon.

"We wanted to have something kind of big to give back to the community in recognition of our 250th year," said Rachel Roehrig, of Ligonier, who co-chairs the event. "The parade is quality entertainment and it's one of the best in southwestern Pennsylvania."

Sunday's highlight will be Dr. Lawrence John Forbes Keppie, a descendant of Gen. Forbes. He will assess the troops for the duration of each battle demonstration and present them with memorial 250th anniversary Fort Ligonier medals. Dr. Keppie's stay is sponsored by the Ligonier 250th Committee.

Though Fort Ligonier Days is a great source of entertainment, it also is a boost to businesses in and around Ligonier.

The weekend impacts local public safety, too. Ligonier Borough police run a detour from about 9 a.m. to 7 p.m. because of increased traffic, and the whole weekend requires an additional 100 man hours, Chief John Berger said. A lot of other people also contribute to making the event run smoothly.

"We use fire and police from Indiana, Somerset and Cambria County and military police for Saturday and Sunday," Chief Berger said. "We have veterans and everyone who works here has done it for so long.

"The Ligonier Borough Department of Public Works cleans up and on Monday morning, it's like nothing happened."