Answer:
Through the many wars and peace congresses of the 18th century, European diplomacy strove to maintain a balance between five great powers: Britain, France, Austria, Russia, and Prussia. At the century’s end, however, the French Revolution, France’s efforts to export it, and the attempts of Napoleon I to conquer Europe first unbalanced and then overthrew the continent’s state system. After Napoleon’s defeat, the Congress of Vienna was convened in 1814–15 to set new boundaries, re-create the balance of power, and guard against future French hegemony. It also dealt with international problems internationally, taking up issues such as rivers, the slave trade, and the rules of diplomacy. The Final Act of Vienna of 1815, as amended at the Congress of Aix-la-Chapelle (Aachen) in 1818, established four classes of heads of diplomatic missions—precedence within each class being determined by the date of presentation of credentials—and a system for signing treaties in French alphabetical order by country name. Thus ended the battles over precedence. Unwritten rules also were established. At Vienna, for example, a distinction was made between great powers and “powers with limited interests.” Only great powers exchanged ambassadors. Until 1893 the United States had no ambassadors; like those of other lesser states, its envoys were only ministers.