Complex sentence: This convocation was one of the events that transformed the general economic and political "malaise" of the country into the French Revolution, which began in June 1789, when the Third Estate unilaterally declared itself the National Assembly.
Split into simpler sentences: This convocation was one of the events that transformed the general economic and political "malaise" of the country into the French Revolution. In June 1789, the Third Estate unilaterally declared itself the National Assembly.