North Korea's claim that it had tested a hydrogen bomb on Wednesday caused concern all around the world. While it was North Korea's fourth test of a nuclear weapon, the use of a hydrogen bomb would suggest a step up from the countries' nuclear program.
To put it in a historical perspective, the chart below shows how it compares to some of the most powerful nuclear tests from other nations below:
However, this second chart is perhaps a better indication of why this test causes so much concern.
North Korea's nuclear program may be nascent and Pyongyang could well be lying about its capabilities – but North Korea is the only country in the world currently carrying out nuclear tests. It has continued to pursue nuclear weapons, despite considerable international politics and economic pressure.
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