The heat must have added mightily to the misery of General Edward Braddock's army as it cut its way through the forests of southwestern Pennsylvania toward the Forks of the Ohio in summer 1755. Being a British soldier in the eighteenth century was never easy, but being one in Braddock's army must have seemed like a cruel sentence for some uncommitted crime. In addition to the brutal discipline that British officers inflicted on their men to maintain order, soldiers had to endure backbreaking labor while living on insufficient and spoiled provisions.

In many respects, an eighteenth-century army was a small city on the move. In addition to officers and soldiers (many of whom brought along their families), it included civilian laborers and teamsters, servants and slaves, and female camp followers (typically at a ratio of one for every ten soldiers) who worked as cooks, nurses, and washerwomen. Braddock's army proceeded at a snail's pace because it had to build a road through the wilderness wide enough to accommodate this population, as well as the wagons and draft animals carrying siege artillery and supplies. The daunting elevations of western Pennsylvania added to the labor, requiring long switchbacks up and down the sides of hills and mountains so that draft animals could handle them. A soldier in Braddock's army was more likely to spend his days wielding an axe than a gun, making war against trees rather than French or Indian enemies.

Braddock had arrived in North America in spring 1755, commanding two Irish regiments sent by the Crown to dislodge the French from the Ohio Country. He immediately fell into difficulty with the colonial Americans who were supposed to assist him: colonial assemblies balked at appropriating money to provision his troops, merchants bickered over supply contracts, and colonial governors gave competing advice about the best route west. In a conference convened at Fort Cumberland in Maryland, the starting point of Braddock's Road to the Ohio, the General alienated his potential Indian allies by refusing to promise them security in their homelands once the French were expelled from the Ohio Country. All but a handful of the Ohio Indians who had come to meet Braddock were unimpressed by what they saw and abandoned his enterprise on the spot.

Braddock left Wills Creek on the Potomac River in Maryland in early June, leading an army of 2,500 men to lay siege to Fort Duquesne, the French post on the Ohio River, along the same route George Washington had followed to his humiliation at Fort Necessity the year before. Finally, on the morning of July 9, Braddock and his men could sense that their goal was within reach. The flying column, which had moved ahead of the support column by traveling without heavy baggage, had just crossed the Monongahela River and moved within ten miles of Fort Duquesne. No doubt, Braddock's superior force would soon force the French at Fort Duquesne to capitulate. Braddock's men proceeded confidently, right into a French and Indian ambush that decimated their ranks. Two-thirds of Braddock's flying column were killed or wounded that afternoon. George Washington, serving as Braddock's aide-de-camp, had two horses shot out from underneath him, and four bullets passed through his clothing. Braddock himself stayed in the saddle in the heat of the battle, trying to rally his troops until he was wounded in the side.

Braddock died of his wound a few days later. Befitting the futility of his expedition, he was buried in the middle of the road his men had built, so that the trampled earth left behind by the retreating army would disguise the grave and prevent the enemy from claiming his remains as a war trophy.

Braddock's Defeat and his army's abandonment of the frontier had profound consequences for the people of Pennsylvania. The colony say its peace evaporate overnight. Its defenselessness was exacerbated by a three-way contest for political power that paralyzed Pennsylvania's government. The proprietary party, made up of the Penn family's supporters and agents, was chiefly concerned with limiting the Penn family's financial liabilities in the colony while wringing maximum profit from land sales. The anti-proprietary party, led by Philadelphia's prominent Quaker families, resented the Penn family's refusal to allow taxation of its proprietary lands and also refused to appropriate money for a militia or frontier fortifications because of the Quaker ethic of non-violence. The Scots-Irish and German settlers of the frontier, who bore the brunt of the French and Indian raids, grew frustrated with stalemate between the proprietary and anti-proprietary parties but were unable to break it because they were underrepresented in Pennsylvania's government. The eastern counties sent 26 representatives to the colony's Assembly; the equally populous western counties sent only 10.

The political stalemate was broken in 1756 when the Penn family agreed to donate money for provincial defenses and the Assembly appropriated money to raise a militia. The government declared war on the Indians and offered bounties for their scalps, prompting many Quaker representatives in the Assembly to resign rather than compromise their pacifist principles. Western Pennsylvanians such as James Burd and John Armstrong took commissions as officers in the new militia and recruited men and built fortifications in the frontier counties, including Fort Loudon, Fort Lyttelton and Fort Shirley. The militia claimed victory when it destroyed the Delaware village of Kittanning in 1756, but French-allied Ohio Indians continued to kill settlers, burn homesteads, and take captives, such as Mary Jemison, with impunity.

Between 1755 and 1758, the history of European-Indian relations in Pennsylvania suddenly and brutally reversed itself. Once a common refuge for Indians, who had been dispossessed by colonial populations elsewhere, Pennsylvania became the seat of a virulent strain of Indian-hating that would animate the darkest episodes in the conquest of the American West. Braddock's ill-fated march to the Ohio served as the catalyst for a conflict that would forever alter the course of Pennsylvania's and America's history.