Final answer:
George Washington was the lieutenant responsible for defeating a French reconnaissance team at the Battle of Jumonville Glen, marking a significant event in the French and Indian War.
Step-by-step explanation:
The lieutenant who defeated a small reconnaissance team in the first engagement of the French and Indian War, resulting in the death of 10 French soldiers in southwest Pennsylvania, was George Washington. At just 22 years old, Washington, who worked as a surveyor and whose family had ties to the Ohio Company, commanded Virginians to fire upon the French near what is now Uniontown, Pennsylvania. This incident, known as the Battle of Jumonville Glen, is considered a catalyst event that subsequently sparked the larger conflict between Britain and France. Later, George Washington also infamously surrendered Fort Necessity to the French and their Native American allies, which became another significant event in the early stages of the war.