Recent warlike threats by North Korea are to force South Korea to change its policies toward the communist country, Seoul\'s former top security official said Thursday.Chun Yung-woo, who served as the top presidential security adviser under former President Lee Myung-bak from 2010 to February this year, also played down security fears, noting that North Korea has almost never staged a military strike on the South while delivering streams of verbal attacks.Angered by the latest U.N. sanctions that punished North Korea for conducting its third nuclear test in February, the North has in response declared a \"state of war\" against South Korea, announced that it would restart a mothballed plutonium-producing reactor, threatened to carry out a nuclear attack against the U.S. and suspended operations at the inter-Korean industrial park.The South Korean and U.S. militaries are on high alert with North Korea expected to test-launch at least one mid-range ballistic missile in the coming days