Will the growing competition between China and the United States inevitably lead to military conflict? One leading American academic created huge attention when in 2017 he posed the idea of what he called a "Thucydides Trap". Drawing on the work of the ancient Greek historian, he warned that when a rising power (Sparta) threatens an existing power (Athens) they are destined to clash, unless both countries change their policies. He warned that the same pattern could play out with the US and China. Since then, President Trump has engaged in combative rhetoric over trade, while China has fast been modernising and upgrading its military. BBC Diplomatic Correspondent Jonathan Marcus considers whether Washington and Beijing can escape the trap - or whether the growing economic, strategic and technological rivalry between the two nations will inevitably end in conflict.