Kenneth Waltz was the most influential international political theorist of the second half of the 20th century. His work defined the contemporary Realist approach to the study of international politics. It spanned international theory (and particularly the creation of a general theory of international politics), international political economy and nuclear deterrence. Much of what has been done in international political theory since the 1970s can be seen as an attempt to build upon, or gainsay, Waltz's contributions, his work shaping scholarship for decades, and still doing so today.