World War III to start over N.Korea sinking of S. Korea warship?

Okay so I herd that South Korea has proof that North Korea was behind the sinking of one of there battleships back in March killing a lot of sailors etc.

if South Korea reacts will this be the start of the third world war?
Update: okay it wasent a "threat" it was an actual attack says South Korea why dont you actually read my question first
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