George W Bush invaded Iraq to remove its - ultimately non-existent - weapons of mass destruction. Barack Obama used cyber weaponry and sanctions to deter Iran from building its own atomic bomb. Now Donald Trump faces North Korea, but stopping its nuclear and missile programme may prove impossible, creating what may be his first and perhaps defining international crisis.
Trump has been left to confront North Korea’s nuclear activities because his predecessors failed to manage them. The regime in Pyongyang, meanwhile, continues to build ever more dangerous weapons systems. Washington’s foreign policy establishment has a host of disagreements with Trump.