One of the key reasons for the obsolescence of war is globalization. Globalization has reduced the incidence of war in at least three wars. First, state no longer need to make economic gains by conquest because globalization offers a cheaper and easier route to national prosperity in the form of trade. Second, by significantly increasing levels of economic interdependence, globalization makes war almost unthinkable because of the high economic costs involved (trade partnerships destroyed, external investment lost, and so on). Third, trade and other forms of economic interaction build international understanding and so counter insular (and possibly aggressive) forms of nationalism.