III.

Imperial Overstretch and the Decline of Great Powers

The network of relations between powerful states that constitute a great-power system first emerged in Europe during the 16th century and solidified during the Thirty Years’ War (1618-1648). At the conclusion of this war, the Peace of Westphalia established the principles that have shaped modern international relations. Foremost among these principles is sovereignty, the respect for the political independence and territorial integrity of states. Since the Peace of Westphalia, the great powers have maintained a balance of power—preserved through shifting alliances and recurrent wars—that generally prevents one state from conquering the others.

The great powers of 16th-century Europe were England, France, Spain, Austria, and the Ottoman Empire. The Habsburg family ruled Austria and Spain. Habsburg power peaked in the late 16th century when Spain conquered Portugal. But the Thirty Years’ War resulted in the defeat of the Habsburgs by a coalition of nations, including France, Sweden, and the German principalities. At the end of the war, The Netherlands assumed dominance of international trading routes and joined the ranks of the great powers, displacing Spain.

Spain’s decline as a great power dated from the beginning of the 16th century, when it experienced a string of costly wars against France and a failed attempt to invade England. The collapse of Spanish power offers an example of imperial overstretch, the fate that befalls great powers when they extend their influence beyond what their size and capabilities can sustain. The Netherlands declined in power in the 18th century when its commercial and maritime rivalry with Britain led it into a series of debilitating wars. In the 20th century, Britain and France declined as great powers when they held onto their far-flung colonial empires for too long.