But perhaps the most important decision they will make for overall human history is what to do about autonomous weapons systems (AWS), aka "killer robots." The new president will literally have no choice. It is not just that the technology is rapidly advancing, but because of a ticking time bomb buried in US policy on the issue.

In 2012, the Obama administration created Department of Defense Directive 3000.09, which sets policy on how the Pentagon handles the questions of this new technology. However, the directive has a 5-year limit, meaning that Hillary Clinton or Donald Trump will need to decide what the US policy on killer robots will be within the first year of their term.