these others to counterbalance it; and his assumption was that these
other Powers would naturally combine for the purpose of redressing the
balance and preserving the peace. But a simple balance between two
opposing forces is a very different thing. If there are only two, you
have no combination on which you can rely to counteract the increasing
power of either, and the slightest disturbance suffices to upset the
balance. Castlereagh's whole scheme therefore presupposed the continued
and permanent existence of some five or six great Powers always
preserving their independence in foreign policy and war, and
automatically acting as a check upon the might and ambition of any
single State.


THE CHANGE SINCE CASTLEREAGH

Now, it was this condition, essential to the maintenance of
Castlereagh's Balance of Power, which completely broke down during the
course of the nineteenth century. Like most of the vital processes in
history, the change was gradual and unobtrusive, and its significance
escaped the notice of politicians, journalists, and even historians. Men
went on repeating Castlereagh's phrases about the Balance of Power
without perceiving that the circumstances, which alone had given it
reality, had entirely altered. The individual independence and automatic
action of the Great Powers in checking the growing ambitions and
strength of particular States were impaired, if not destroyed, by
separate Alliances, which formed units into groups for the purposes of
war and foreign policy, and broke up the unity of the European system,
just as a similar tendency threatens to break up the League of Nations.
There was a good deal of shifting about in temporary alliances which
there is no need to recount; but the ultimate upshot was the severance