The main cause of the American Revolutionary War was the growing discontent among the American colonies regarding British taxation and lack of representation in Parliament. The imposition of taxes, including the Stamp Act and Townshend Acts, without colonial input fueled resentment, leading to protests and the rallying cry of "no taxation without representation." Additionally, British attempts to control colonial governance and economic practices ignited widespread opposition. The colonies sought to assert their rights and independence, culminating in the Declaration of Independence in 1776 and ultimately leading to a war for liberation from British rule.