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Once again, North Korea has raised the stakes and the rest of the world is wondering what to do about it. This time it seems to have been a hydrogen bomb that's been tested - massively more powerful than the atomic bombs they have tested in the past.

The United Nations Security Council is holding an emergency meeting today and President Trump has turned to Twitter again, this time he is criticising South Korea for its "talk of appeasement".

Danny Russel was assistant secretary of state for East Asia under President Obama and President Trump. He gives his perspective on the increasing aggression exhibited by Pyongyang.

(Image: South Korea missile drill. Credit: EPA)