The South Korean and US militaries staged joint river-crossing drills in the border county of Yeoncheon on Saturday as part of their annual key springtime exercise aimed at enhancing interoperability between the allies. The field training coincided with North Korea firing around 10 ballistic missiles toward the East Sea earlier in the day. The North's missile launch came in an apparent muscle-flexing against the Seoul-Washington joint military exercise. The training took place on the Imjin River