Have ranged from two early wars to competition for world markets

American Revolution

John Trumbull's painting depicting The Death of General Warren at the Battle of Bunker Hill, 1775.

See also: American Revolution and American Revolutionary War
The Thirteen Colonies gradually obtained more self-government.^[14] British mercantilist policies became more stringent, benefiting the mother country which resulted in trade restrictions, thereby limiting the growth of the colonial economy and artificially constraining colonial merchants' earning potential. The sums were small but Parliament insisted that it was in final command and could impose taxes at any time. Tensions escalated from 1765 to 1775 over issues of taxation without any American representation in Parliament. Starting with from the Boston Massacre of 1770 when seven men of the 29th Regiment of Foot opened fired on a crowd of hostile Bostonians who were harassing them, talk of revolution consumed the outraged colonists. Parliament imposed a series of taxes such as the Stamp Act, and later the Tea Act of 1773, against which an angry mob of colonists protested in the Boston Tea Party by dumping chests of East India Company tea into Boston Harbor. Parliament responded by passing what the colonists termed the Intolerable Acts in 1774, which were designed to strip away self-government in Massachusetts. The thirteen colonies stood together. When the first shots fired in the Battles of Lexington and Concord in 1775 there began the American War of Independence. The Patriots then took slowly control of all thirteen colonies, ejecting all British officials by mid-1776. While the goal of attaining independence was sought by a majority known as Patriots, a minority known as the Loyalists wished to remain as British subjects loyal to the king. When the Second Continental Congress convened in Philadelphia in May 1775, deliberations conducted by notable figures such as Benjamin Franklin, Thomas Jefferson, John Hancock, Samuel Adams, and John Adams resulted in a decision for full independence. Thus, the Declaration of Independence, unanimously ratified on July 4, 1776, was a radical and decisive break. The United States of America became the first colony in the world to successfully achieve independence in the modern era.^[15] According to R. R. Palmer the new American nation: inspired the sense of a new era. It added a new content to the concept of progress. It gave a whole new dimension to ideas of liberty and equality made familiar in the Enlightenment. It got people into the habit of thinking more concretely about political questions, and made them more readily critical of their own governments and society. It dethroned England and set up America as a model for those seeking a better world.
In 1775, the Patriots established the Continental Army as a defense force. The British Army returned in force in August 1776, and captured New York City, which became their base until the war ended in 1783. The British, using their powerful navy, could capture major ports, but 90% of the Americans lived in rural areas where they had full control. After the capture of a British invasion force moving down from Canada in the Saratoga campaign of 1777, France entered the war as an ally of the US, and added the Netherlands and Spain as French allies. Britain suffered casualties which it could not replace and had no major allies and few friends in Europe. The British strategy was then refocused on the South, where they expected large numbers of Loyalists would fight alongside the regulars. Far fewer Loyalists took up arms than Britain needed; royal efforts to control the countryside in the South failed.