SHILOH, Tenn. (AP) _ The echo of musket fire swept across rolling fields Sunday as 6,000 Civil War buffs transformed into Civil War soldiers staged a remake of one of the bloodiest battles on American soil.

Cavalry companies charged into the fray with swords and pistols drawn while 66 cannon sent clouds of smoke and waves of thunder across the battlefield.

''When the shooting starts and your adrenaline gets up, you get just as excited as if it were real,'' said William Carrington of Durham, N.C., serving as a lieutenant with the 19th Alabama Infantry.

The show, watched by about 40,000 people perched on hills, the first day of what had been a two-day fight 125 years ago.

The real battle began on April 6, 1862, when 40,000 Confederate troops led by Gen. Albert Sidney Johnston surprised an equal number of Union soldiers under the command of Gen. Ulysses S. Grant.

The Union army, marching south after victories at Fort Donelson and Fort Henry on the nearby Tennessee River, had decided to rest and drill in west Tennessee near Shiloh Church.

Confederate troops marched up from Corinth, Miss., about 20 miles south. By the time the battle ended, more than 100,000 men had joined the fight, and 23,000 of them were killed or wounded.

At the time it was the largest battle fought in the United States.

Sunday's event was organized by the Shiloh Re-Enactment Association Inc., which said requirements for proper period dress and weapons were strictly enforced. The soldiers, wearing replicas of Civil War uniforms, were armed with 1860s-era weapons or replicas. Cavalrymen provided their own mounts.

The location for the re-enactment was a 600-acre field near the original battleground, now a national park about 100 miles east of Memphis. On Saturday, the participants from 47 states and five foreign countries practiced marching, turning, advancing with fixed bayonets and other war tactics of the day.

Re-enactment organizers had to deal with matters more mundane than combat, such as parking and traffic control.

Ken Chrestman, who spent two years planning and organizing the re-creation, said thousands of dollars were spent on insurance, permission to use the land had to be secured, and 120 ''porta-johns'' were ordered. The Re-Enactment Association hoped to recoup the $50,000 cost by charging spectators $3 for tickets.

''In many ways, it's like a play,'' Chrestman, a 34-year-old investment banker, said recently. '''But what we do is a lot more serious than a play. It's history re-created so people can see and understand what happened 125 years ago. It's awfully hard to smell black powder between the pages of a history book.''