JOHNS ISLAND -- Former slaves fought their old masters, both thirsty to kill. The Battle of Bloody Bridge was so murderous that the wounded were bayoneted and thrown into pits, so the story goes.

This is the Civil War ambush you likely have never heard of, in a place you likely have driven right by. Some 2,000 South Carolina calvary militiamen withstood four times as many Union soldiers for three days in suffocating summer swelter in a tidal swamp. The militiamen were largely the families of the sea island plantations, who had evacuated as the Union advanced.

The Union forces were partly U.S. Colored Troops, many of them from those plantations. The battle, also called Burden's Causeway, took place this week in July 1864.

"Thousands of people, separated by a shallow water, malarial mosquitoes and snake-infested swamp," said Kipp Valentine, a 1st South Carolina Cavalry Confederate re-enactor who grew up and lives along the creek. "According to the legend, the wounded were bayoneted by old men and boys and then thrown into mass graves."

The pitched battle was a microcosm of the war -- full of passions, bullheadedness and blunders. It's been overshadowed by the larger legacies of Fort Sumter and the battle for Charleston. But it's not forgotten. Along what is today River Road on Johns Island, a historic marker sits on the site, just north of Charleston Executive Airport.

And, as Valentine says, he can go to church on Sunday and see the family faces of the men who fought there.

"It certainly happened in an interesting location. It's right in the middle of resort communities now," said William Hamilton III, a Charleston lawyer who has researched the battle. "It was two groups trying to kill each other for some time. It shows the brutalizing effect of a long war."

On July 2, forces landed on Seabrook Island, Legareville on Johns Island and Rockville to the southwest. They hoped to outflank the dug-in Confederate defenses on Morris Island and Folly Beach, as part of an all-attack on the city. It was one of five simultaneous assaults around Charleston, as Union ships bombarded both the city and Fort Sumter guarding the harbor.

"They brought horses, artillery, baggage wagons, ambulance wagons, the whole nine yards," Valentine said.

Brig. Gen. John Hatch planned to cross Johns Island and then the Stono River, to seize James Island, according to accounts. His forces looted an abandoned plantation down to "the doors off the hinges," Valentine said, then took up a slow march in the dizzying heat. They made one, very big mistake.

They marched right past Fort Trenholm, evidently unaware the Stono River fortification and its cannons were there, right about where today's airport runway ends.

"It's just classic. One of the things you don't do is leave an enemy fortification on your behind," Valentine said.

In the field just to north, the troops reached the pilings where the planks had been torn from a tiny bridge where a non-descript creek turned to swamp. Waiting for them were the Stono Scouts local cavalry militia and two other Confederate forces, about to be joined by two more. They were dug into rifle pits along the creek below. Along Burden's Creek today, you can see the remnants of what's thought to have been those pits.

Union sharpshooters opened fire and were blasted back. That afternoon, 1,000 Union troops including the 26th U.S. Colored Troops attacked and took the rifle pits, scattering the Confederates until reinforcements moved in screaming rebel yells. The Confederates retook the pits.

The next day cannon opened fire from Battery Pringle on James Island and skirmishes continued. But that night, the Confederates abandoned the rifle pits and moved back to pits in woods at the edge of the field. On July 9, with reinforcements of his own, Hatch felt he had the numbers to attack again. He didn't.

His men crossed the creek, fixed bayonets and attacked in formation across the field. A flare went up. The cannon from Fort Trenholm had been turned around and sighted in. In the pre-dawn dark, cannon balls fell and a Confederate skirmish line opened fire at the woods and attacked, pushing the troops back across the open field in black smoke too thick to see. Hundreds died. Hatch's troops slipped away that night, evacuating the island.

"And they never bothered Farmer Jones' carrots again," Valentine said.

For his part, Maj. Gen. H.W. Halleck, Hatch's superior, made the best of a siege fiasco that killed, wounded or lost track of more than 300 men and saw three die of sunstroke -- officially, according to a battle report that reads like a victory.

"Our advance upon Johns and James Islands caused the enemy to accumulate troops to oppose our further progress," Halleck wrote headquarters. "The late movements have had a decidedly beneficial effect on the troops, both white and black."

Valentine's take on it is a little different.

"They (Confederate troops) just rained them full of shot and shell," he said. "It was a brutal thing."

Reach Bo Petersen at 937-5744 or bpetersen@postandcourier.com.