Conclusion
There is nothing sacred about an existing alliance, no matter how successful or
long-lived it has been. When domestic preferences or external conditions
change, existing commitments may no longer be desirable and states are more
likely to seek other arrangements. Yet new conditions need not provoke an
instantaneous reaction, and alliances formed in one context may well endure
under quite different circumstances. The Austro-French alliance lasted from
1756-92; the Austro-German 'Dual Alliance' persisted from 1879 until the end
of the First World War, and the Anglo-Portuguese alliance survived, by some
estimates, an extraordinary 600 years.46
Alliances can endure despite farreaching
shifts in the internal or external environment, if only because national
leaders are often eager to reduce uncertainty during a period of rapid change.