Dominic Cummings admires military strategists more than political gurus. He likes to quote the ancient Chinese general Sun Tzu who argued that the “supreme art of war is to subdue the enemy without fighting”. The way to achieve that, the prime minister’s senior adviser once explained, is by confusing and demoralising your foe through “disorientating moves, feints, bluffs”. This is exactly what Boris Johnson has done with his decision to prorogue parliament and to threaten Tory rebels with expulsion from their party but politics is not a war. Democracy is about persuasion rather than obliteration and there are rules underpinning political conflict that don’t apply in military combat. The prime minister seems to have forgotten that, far from being the nation’s commander-in-chief, he is only