The US military yesterday successfully shot down a medium-range ballistic missile  in a test of a new interceptor system. It is co-developed with Japan and has been dogged by previous failures.<br />''    <br />'' The Missile Defense Agency (MDA) said  that sailors aboard the USS John Finn successfully detected, tracked and targeted the rocket with an SM-3 Block IIA missile during a test off the west coast of Hawaii. <br />''  <br />'' The successful operation comes after two failed intercept tests, in June 2017 and January 2018.<br />'' <br />