The United States' aircraft carriers USS Carl Vinson (No. 70) and USS Ronald Reagan (No. 76) sailing in side by side in waters off the Korean peninsula in the Sea of Japan yesterday. The carriers and their strike groups were conducting a joint exercise with the Japanese destroyers Hyuga and Ashigara in an apparent show of force after the latest North Korean ballistic missile test on Monday. Pyongyang has now conducted a dozen ballistic missile tests this year, in defiance of UN sanctions warnings and amid fears that it may be preparing for another nuclear test. Washington described the drill as "routine training", even as the US and Japan step up their rhetoric with an eye to stopping North Korea's missile and nuclear programmes..