From Wealth to Power argues that states are not simply security-seekers that expand in response to actual or perceived threats; rather, states expand when they see opportunities to extend their influence and when they have sufficiently strong central governments to translate desire into action. In the conclusion, Zakaria writes (p.185):
A scholar looking at great-power behavior over time -- even in a secure, relatively benign nation like the United States -- must conclude that states seek more than mere security: they seek influence over the international environment. And the more powerful they become, the more influence they seek.Let's put aside the valid point that the U.S. was not "relatively benign" in the eyes of the native Americans or Filipinos whom it conquered, and focus on the main assertion: that states seek "influence over the international environment." This raises the question: why? What does it "do" for states, how does it benefit them, to have such "influence"? In the case of the U.S., one answer might be that "influence" resulted in overseas markets for capitalists. This is the answer given by the Wisconsin School (William Appleman Williams, et al.). But Zakaria, though he acknowledges a debt to certain writings of this school (p.51), clearly does not go in that direction.
Does he answer the question at all? Not as I recall, though I did not re-read the whole book. But if he were to have answered it, it seems to me he would have had a couple of options. He could have gone with Mearsheimer and said that expansion is the surest way to ensure security in an 'anarchic' world. Or he could have gone with Schumpeter and said that expansion is an atavistic impulse, an 'objectless disposition'. Neither of these is very satisfactory. A third possible answer, at least in the case of the U.S., would focus on culture and ideology (Social Darwinism, white man's burden, and all that), and Zakaria does mention this in passing (pp.135-36). Finally, one could look at the role of domestic pressure groups and parties. But as it is, the question why states seek "influence" rather than "mere security" is left hanging.
It may be worth noting that the very end of the book is guardedly optimistic. Zakaria does not talk of the obsolescence of great-power war, but he does note its "long absence." These are the concluding sentences (p.192):
The long absence of great-power war and the growth of the global economy have weakened the state and intertwined it in structures that will make the once-straightforward rise and fall of great powers a complex, friction-filled process. These complications may create greater uncertainty for scholars, but they could help blunt the otherwise aggressive temperament of great powers and tame the fierce nature of international life.