The two centuries since the Congress of Vienna have seen the gradual codification by the international community of the “rules of the game” for guiding interstate relations, even between unfriendly countries. Their basic premise has been the formula “don’t do to me what you don’t want me to do to you”. However, technological advances mean that today those rules are being dangerously undermined. The international system is at risk.

After the age of Metternich, Talleyrand and Castlereagh, elaborate understandings developed about the transition from formal peace to war. These involved carefully scripted exchanges of diplomats, rules about the treatment of prisoners of war and eventually even a shared definition of war crimes. Implicit in all this was the notion that while war and peace are fundamentally different conditions, both still need rules of conduct.

In more recent times, the use of nuclear weapons has made the distinction between the two more dramatic. The destructiveness of these weapons was without precedent but paradoxically that encouraged more cautious behaviour on the part of the states that possessed them. The existence of such weapons also created a new global hierarchy with a few nuclear states at the top and the rest below.