The strategic objective of the Forbes Expedition, like the earlier unsuccessful Braddock Expedition early in the war, is the capture of Fort Duquesne, a French fort constructed at the confluence of the Allegheny and Monongahela Rivers in 1754 (site of present-day downtown Pittsburgh, Pennsylvania's Golden Triangle).

Forbes commands between six thousand and eight thousand men, including a contingent of Virginians led by George Washington.

Forbes, very ill, does not keep up with the advance of his army, but entrusts it to his second in command, Lieutenant Colonel Henry Bouquet, a Swiss officer commanding a battalion of the Royal American Regiment.

The expedition methodically constructs a road across what is now the southern part of Pennsylvania's Appalachian Plateau region, staging from Carlisle and exploiting the climb up via one of the few southern gaps of the Allegheny through the Allegheny Front, into the disputed territory of the Ohio Country, which is at this time a largely depopulated native tributary territory of the Iroquois Confederation.

This well organized expedition is in contrast to a similar expedition led by Edward Braddock in 1755 that ended in the disastrous Battle of the Monongahela.

Working for most of the summer on the construction of the road, periodic fortified supply depots, the expedition had not come within striking distance of Fort Duquesne until September 1758.

A reconnaissance force had been soundly defeated in the Battle of Fort Duquesne in mid-September when its leader, Major James Grant, had attempted to capture the fort instead of gathering information alone.

The French, their supply line from Montreal cut by other British actions, attack one of the expedition's forward outposts, Fort Ligonier, in an attempt to either drive off the British or acquire further supplies, but are repulsed in the Battle of Fort Ligonier.

The Treaty of Easton concluded on October 26, 1758, causes the remnants of the Lenape (Delaware), Mingo, and Shawnee tribes in the Ohio Valley to abandon the French, and sets up the conditions that ultimately will force them to move westward once again.