When British commander Lord Cornwallis surrendered his army to American and French forces at Yorktown on Oct. 19, 1781, the Revolutionary War ended in the east.

Violence continued, however, on the Pennsylvania frontier for several more years.

American attempts to keep most Iroquois, Delaware and Shawnee Indians neutral had collapsed by 1778. Casualties quickly rose on both sides, claiming mostly civilians across wilderness areas that became Western Pennsylvania, Ohio and West Virginia.

Most of the fighters allied with the Americans, Native American and the British were irregulars and saw themselves as answerable to no military codes.

Poorly trained Pennsylvania militiamen, for example, killed Shawnee chief Cornstalk in 1777. Early the next year, an American expedition from Fort Pitt to destroy British supply depots along the Cuyahoga River failed. While returning to the Forks of the Ohio, some of those troops killed Delaware women and children in what was called the "Squaw Campaign."

The worst incidents happened in 1782, which some historians have called "The Year of Blood."

Writing to his wife on April 12, 1782, William Irvine, the new American commander of Fort Pitt, described the murder of about 100 Delaware Indians who had converted to Christianity. They had been living west of Fort Pitt, at the Moravian settlement of Gnadenhutten, in what is now Tuscarawas County, Ohio.

"A number of the Country people had just returned from the Moravian towns, about 100 miles distant, where, 'tis said, they did not spare either age or sex," Mr. Irvine wrote. "What was more extraordinary they did it in cool blood, having deliberated three days, during which time they were industrious in collecting all hands into their Churches." While their victims sang hymns, the militiamen killed them with blows to the head from mallets. "Many children were killed in their wretched Mother's arms," he told his wife.

His letters are collected in "Fort Pitt and Letters from the Frontier," published in 1892 by J.R. Weldin & Co.

Irregular forces were responsible for violence closer to home, Mr. Irvine wrote, claiming there was little his troops could do to stop it. "[O]n the morning before my arrival here a party of Militia attacked some friendly Indians ... at the very nose of the garrison, on a small island in the River." The frontiersmen killed several Native Americans, imprisoned Continental Army troops who tried to stop them and threatened to scalp Col. John Gibson, Mr. Irvine's predecessor as commander at Fort Pitt.

As a teenager, Mr. Gibson had been captured by Mingos and lived with the tribe for several years. His link with Indians tainted him in the eyes of many settlers.

Mr. Irvine concluded that standards of morality had become very different for those on the frontier. "People who have had Fathers, Mothers, Brothers or Children butchered, tortured, scalped by the savages [reason] very differently on the subject of killing the Moravians [than do] people who live in the interior part of the country in safety," he wrote his wife.

The Indians got partial revenge for Gnadenhutten a few months later when Col. William Crawford led an expedition of almost 500 militiamen from Fort Pitt west into present-day Ohio. Surprised by an Indian force of near equal size, the American army fell apart. About 70 militiamen were killed or captured, with all but a few of those taken prisoner soon slain.

While Col. Crawford had not been present at the Gnadenhutten massacre, many of his men had taken part, and the Delawares held him responsible. "The unfortunate Colonel ... was burned and tortured in every manner they could invent," Mr. Irvine wrote in a letter he sent to George Washington from Fort Pitt on July 11.

He also informed George Washington that an eyewitness -- Dr. John Knight -- recognized Simon Girty as present when the Indians killed Col. Crawford. Girty family members owned land in what is now Ross; Girty's Run is named for them.

Mr. Girty, who like Mr. Gibson had been captured and lived among the Indians, had served as a translator at Fort Pitt after the French and Indian War. During the Revolution, however, he sided with the British and their Native-American allies. Mr. Irvine wrote that Dr. Knight told him that Col. Crawford "begged of Girty to shoot him, but he paid no regard to the request." Mr. Girty later said that he would have been killed himself if he had interfered.