International monetary and financial systems may not be immutable, but nor do they change often. That is why the upheaval spurred by US President Donald Trump’s trade and tariff war is so remarkable – and difficult to decipher. To figure out what is going on, it is worth revisiting Charles P. Kindleberger’s theory of hegemonic stability, which he spelled out in his book The World in Depression: 1929-1939. Kindleberger’s theory essentially states that an open and stable international system depends on the presence of a dominant world power.