What event led to France joining the American Revolution?

The event that led to France formally joining the American Revolution was their recognition of the United States in 1778. This recognition was a pivotal moment as it not only legitimized the American cause in the eyes of a major European nation, but it also paved the way for France to enter into a military alliance with the Americans. The motivations for France's support included a desire to weaken Britain, their long-time rival, and to promote their own interests in the context of global power dynamics.

By recognizing the United States as an independent nation, France committed to providing military and financial assistance, which proved crucial to the American efforts against British forces. This alliance significantly influenced the course of the war and ultimately contributed to the success of the American Revolution, marking a turning point in the conflict.