The primary cause of the American Revolutionary War was the growing dissatisfaction among the American colonists with British rule, particularly regarding taxation and lack of representation in Parliament. Key grievances included the Stamp Act, Townshend Acts, and the Tea Act, which imposed taxes without colonial input. The rallying cry of "no taxation without representation" encapsulated the colonists' frustrations. Additionally, the desire for self-governance and the influence of Enlightenment ideas fueled the push for independence. Tensions escalated with events like the Boston Massacre and the Boston Tea Party, ultimately leading to the outbreak of war in 1775 as colonists sought to assert their rights.