Stephen Sackur speaks to retired US general Ben Hodges, former Commander of the US Army in Europe. The 20th century was in many ways shaped by America’s unrivalled power; two decades into the new century, and it's clear the story arc is shifting. China is projecting its power across the globe, Russia is out to reassert its regional supremacy, and the limits of American power have been exposed from Iraq to Afghanistan. Is the US in danger of losing the race to define the 21st century?