Final answer:
The Revolutionary War was officially started by the battles of Lexington and Concord and the signing of the Declaration of Independence.
Step-by-step explanation:
The events that officially started the Revolutionary War were the battles of Lexington and Concord and the signing of the Declaration of Independence. On April 19, 1775, the colonial militia clashed with British forces in Lexington and then again in Concord, leading to the first shots of the war. This event is known as the "shot heard around the world." Following these battles, the Second Continental Congress met in May 1775 and eventually declared American independence from Britain on July 2, 1776. Two days later, they signed the Declaration of Independence, officially starting the war.