As US President Donald Trump’s supporters massed outside the Capitol last week and sang the national anthem, a line of men wearing olive-drab helmets and body armour trudged purposefully up the marble stairs in a single-file line, each man holding the jacket collar of the one ahead. The formation, known as “Ranger File”, is standard operating procedure for a combat team that is “stacking up” to breach a building – instantly recognizable to any US soldier or Marine who served in Iraq and Afghanistan. It was a chilling sign that many at the vanguard of the mob that stormed the seat of American democracy either had military training or were trained by those who did.