named Robert Jenkins sparked the War of Jenkins' Ear between Britain and Spain. Hundreds of North Americans volunteered for Admiral Edward Vernon's assault on Cartagena de Indias, a Spanish city in South America. The war against Spain merged into a broader conflict known as the War of the Austrian Succession, but most colonists called it King George's War. In 1745, British and colonial forces captured the town of Louisbourg, and the war came to an end with the 1748 Treaty of Aix-la-Chapelle. However, many colonists were angered when Britain returned Louisbourg to France in return for Madras and other territories. In the aftermath of the war, both the British and French sought to expand into the Ohio River valley. The French and Indian War (1754–1763) was the American extension of the general European conflict known as the Seven Years' War. Previous colonial wars in North America had started in Europe and then spread to the colonies, but the French and Indian War is notable for having started in North America and spread to Europe. One of the primary causes of the war was increasing competition between Britain and France, especially in the Great Lakes and Ohio valley. The French and Indian War took on a new significance for the British North American colonists when William Pitt the Elder decided that major military resources needed to be devoted to North America in order to win the war against France. For the first time, the continent became one of the main theaters of what could be termed a "world war". During the war, it became increasingly apparent to American colonists that they were under the authority of the British Empire, as British military and civilian officials took on an increased presence in their lives. The war also increased a sense of American unity in other ways. It caused men to travel across the continent who might otherwise have never left their own colony, fighting alongside men from decidedly different backgrounds who were nonetheless still American. Throughout the course of the war, British officers trained Americans for battle, most notably George Washington, which benefited the American cause during the Revolution. Also, colonial legislatures and officials had to cooperate intensively in pursuit of the continent-wide military effort. The relations were not always positive between the British military establishment and the colonists, setting the stage for later distrust and dislike of British troops. At the