Description:U.S. and South Korean artillery troops are conducting a joint live fire drill on Tuesday. They're testing readiness against a potential North Korean artillery attack on the South. One U.S. artillery battalion and two South Korean artillery units are taking part. The exercise involves the use of the Multiple Launch Rocket System, or MLRS, which provides counter-fire and suppression of enemy air defences, light material and personnel targets at a range of nine to 186 miles.(1:29)