Although it's not expressed explicitly in the brief passage quoted above, MacArthur's remarks seem to refer to nuclear warfare and its corollary, "mutual assured destruction."

For all of human history until the development of the atomic bomb, the nation-state was the most powerful institution participating in human history, and conflicts between nations tended to be won by whoever possessed the most advanced weapons technology. The guys with bows and arrows beat the ones throwing spears, later the inventors of the crossbow beat those still using the longbow, etc. etc. etc.

With the appearance of weapons so terrible that they could destroy their owners as well their owners' enemies, conventional warfare has now become obsolete, and nation-states no longer enjoy their longstanding preeminence.

"Information war" ~ including both terrorism and non-violent resistance ~ has already begun to replace warfare as we have always known it, just as multinational corporations are rapidly replacing political organizations (nations) as the leading actors ~ the most potent forces ~ on the historical stage.

I believe that the world's current state of extreme confusion is largely due to the fact that most "world leaders" (i.e., heads of state) are blind to the fact that this historical paradigm shift has already occured.