doesn't happen, they'll be ready if it breaks out. a war in korea could start like this. volley after volley of north korean artillery raining down on seoul. shows of weapons are pointed at the south korean capital, home of 10 million people. defending it is priority number one for her generals and politicians. the u.s. army granted cnn exclusive access to the 6th battalion 37th field artillery. the workhorse, the alpha 1, also known as steel rain. i get a tour of the multiple launch rocket system. >> it's about being able to provide support fires in a timely manner and being precise at the same time. >> reporter: the mrms can fire