The French – Indian war took place for over seven years, pitting Britain against France to control most of North America. Preceding the war, France had started advancing into the Ohio River valley in the early 1950s, a move that created tension in the British camp. The Britons felt like the French wanted to acquire more territories than they initially had; one such British colony with problems with France occupying the Ohio River Valley was Virginia.
The French built a fort in a strategic location where the rivers Allegheny and Monongahela converged to form the Ohio River in 1754. The British attacked the French bases to weaken them and reduce their dominance in North America by using General Braddock, who was defeated. This first attack by the British would create a string of other conflicts between the two nations.
The British formally declared war against France in 1756 to mark the French and Indian War. Before the war began, Governor Shirley of Massachusetts cruelly sent the French out of the land they occupied to other British territories because he feared they would spark a French uprising in his state. General Braddock and George Washington were the first to be attacked by the French and defeated quickly before they retreated.
Therefore, the leading cause of the war would be the bone of contention on whether the Ohio that the French occupied belonged to the Britons and if the Virginians and Pennsylvanians were allowed to settle and trade in the region. The strings of attacks were used to justify the declaration of war and not the primary cause.