As competition and rivalry between the great powers increase, the overriding challenge for international politics in the first half of the 21st century is to maintain “one world”: one international order to which all states contribute, because they all subscribe to its core set of rules, which give all states the opportunity to build stable and mutually beneficial relations with any other state. Ideally, a concert of the great powers embedded in strong multilateral institutions would play a leading role.
The alternative would be for the world to break apart again as the great powers gradually decouple from each other and try to forge mutually exclusive blocs. This would not be a cold war like the Cold War, since power is distributed more widely today than it was in 1945, when the US and the USSR towered above everybody else and decolonisation had yet to happen. But it would still spell economic crisis and render it impossible to address global challenges such as the climate crisis or a pandemic.
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