From the speech:

"We will not eradicate violent conflict in our lifetimes.  There will be times when nations -- acting individually or in concert -- will find the use of force not only necessary but morally justified... For make no mistake:  Evil does exist in the world.  A non-violent movement could not have halted Hitler's armies.  Negotiations cannot convince al Qaeda's leaders to lay down their arms.  To say that force may sometimes be necessary is not a call to cynicism -- it is a recognition of history; the imperfections of man and the limits of reason."