Friends reunited? Trump and Kim Jong-Un's curious relationship will play out differently this time

Donald Trump and Kim Jong Un met in the Demilitarised Zone last year .

The last meeting did not advance a longed-for deal to get North Korea to give up its nuclear weapons.

Since then, Kim has advanced his missile programme and claims to have successfully tested a hypersonic missile, despite being subject to strict international sanctions.

Pyongyang is no longer as desperate for relief from US sanctions.

Kim Jong Un and Donald Trump met in Vietnam for the first time since the end of the Korean War .

After a year of acrimonious exchanges and brinkmanship, the US president took to Twitter to air his wrath threatening to rain down 'fire and fury' on North Korea .

The liberal South Korean president, Moon Jae-in had been hoping for an icebreaker with Pyongyang .

Trump offered to lift U.S. sanctions if Kim gave up all nuclear weapons, nuclear material and nuclear facilities.

Donald Trump's unorthodox diplomacy reduced tensions for a while, but it did not stop the expansion of Pyongyang 's weapons programme.

As Trump flew back to Washington , the North Koreans took the unprecedented step of holding a press conference.