This episode's headline: Mission Accomplished; Competitive Edge; Battle Lines. The guests include DONALD GREGG, Former Ambassador to South Korea; ELIG HARRISON, Carnegie Endowment; WILLIAM TAYLOR, Center ForStrategic & International Studies; SEN. JOHN McCAIN, [R] Arizona; CORRESPONDENTS: SPENCER MICHELS; ROGER MUDD. Byline: In New York: JAMES LEHRER; In Washington: MARGARET WARNER