Around 1450, the greatest empires and the greatest markets of the world were China, India and the Ottoman empire, while also cultures like the Khmer in Cambodia and the Aztecs in Mesoamerica projected great power and achievements. Europe was a collection of small countries in a constant state of war, a great step back from the civilisation of the Roman empire. 300 years later Europe ruled the world. How was that possible, and how important were viruses and gunpowder, religion and geography?