Michael relinquishes the mechanistic, one-trick-pony policy approaches of his brothers in favor of a “toolbox,” in which soft and hard power are used in flexible combinations and as circumstances dictate. While at various times he sides with Tom (favoring negotiation) or Sonny (favoring force), Michael sees their positions as about tactics and not about ultimate strategy, which for him is solely to ensure the survival and prosperity of the family. Thus, he is able to use Sonny’s “button men” to knock out those competitors he cannot co-opt, while negotiating with the rest as Tom would like. This blending of sticks and carrots ensures that Michael is ultimately a more effective diplomat than Tom and a more successful warrior than Sonny: when he enters negotiations, it is always in the wake of a fresh battlefield victory and therefore from a position of strength; when he embarks on a new military campaign, it is always in pursuit of a specific goal that can be consolidated afterwards diplomatically.
I'm not so sure about this. Isn't Michael the ultimate neo-con, utterly unrestrained by norms or institutions? He's the one that hatches the scheme to kill Sollozzo and his police captain bodyguard, a step that even the hot-headed Sonny initially thinks is beyond the pale. And then at the end of the movie, Michael organizes the ultimate military operation to "settle all family business" by eliminating the heads of the other five families and establishing a Pax Corleone in which the family's power is even more unassailable. This scene brings to mind the reports that in the aftermath of 9/11, Donald Rumsfeld assembled a list of six or seven countries to invade, a settling of U.S. "family business" as it were.