Final answer:
The French and Indian War expanded from a conflict over frontier forts into a larger war due to territorial claims in the Ohio River Valley, escalating tensions from British expansion and French strategic responses, and shifting alliances with Native American tribes.
Step-by-step explanation:
The conflicts over frontier forts between France and Great Britain escalated into the French and Indian War, which stemmed from both nations' claims over the Ohio River Valley. This began when Virginians, including a young George Washington, crossed the Allegheny Mountains and clashed with French efforts to fortify the region with forts in western Pennsylvania. The tension between the British desire to expand and the French strategic defensive response, coupled with trade relationships and alliances with Native American tribes, made the contested area a flashpoint for extended conflict. British victory in this war marked the end of French power in North America, but the subsequent Treaty of Paris in 1763 also significantly affected Native American tribes, who had hoped to benefit from the competition between the two European powers for trade and political leverage.
During the war, the French allied themselves with certain Native American tribes, such as the Huron, to counter British expansion. After the British triumph, the loss of the French as a trading and military partner, together with aggressive British policies and actions, triggered further resistance from Native American tribes, including Pontiac's Rebellion. The British failure to maintain alliances with Native American tribes, as the French had, intensified the difficulties in establishing control over the newly acquired territories. Ultimately, this underlying tension would contribute to further colonial unrest, which precipitated the American Revolution.