NORTH KOREA'S PAST THREATS
North Korea has frequently employed bellicose rhetoric towards its perceived aggressors. The 1994 threat by a North Korean negotiator to turn Seoul into "a sea of fire" prompted South Koreans to stock up on essentials in panic. After US President George W Bush labelled it part of the "axis of evil" in 2002, Pyongyang said it would "mercilessly wipe out the aggressors". Last June the army warned that artillery was aimed at seven South Korean media groups and threatened a "merciless sacred war". There is also a pattern of escalating threats whenever South Korea gets a new leader.
While many observers dismiss the rhetoric as bluster, others warn of "the tyranny of low expectations" when it comes to understanding North Korea, because there have been a number of serious regional confrontations. "If you follow North Korean media you constantly see bellicose language directed against the US and South Korea and occasionally Japan is thrown in there, and it's hard to know what to take seriously. But then when you look at occasions where something really did happen, such as the artillery attack on a South Korean island in 2010, you see there were very clear warnings," Professor John Delury at South Korea's Yonsei university told the BBC.
The North consistently warned that military exercises being conducted in the area would spark a retaliation. Mr Delury argues that misreading Pyongyang's intentions and misunderstanding its capabilities has kept the US and South Korea stuck in a North Korean quagmire.
PICKING APART THE BLUSTER
The latest warning of a pre-emptive nuclear attack was in response to joint military exercises between South Korea and the US rather than sanctions per se. "Any time a nation threatens pre-emptive nuclear war, there is cause for concern. North Korea is no exception, with its recent shift in rhetoric from accusing the US of imagining a North Korean ballistic missile threat, to vowing to use its ballistic missile capabilities to strike the continental US," says Andrea Berger, from the Royal United Services Institute in London.
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BBC News - How potent are North Korea's threats?