The North's army said it had conducted activities simulating attacks on air bases and aircraft, as well as a major South Korean city, to "smash the enemies' persistent war hysteria"The flurry of missile launches included the most ever in a single day, and come amid a record year of missile testing by the nuclear-armed North Korea.The South Korean Navy rescue vessel used an underwater probe to recover the parts, which are being analysed, the official said.The operations also included a launch of two "tactical ballistic missiles loaded with dispersion warheads," a test of a "special functional warhead paralysing the operation command system of the enemy," and an "all-out combat sortie" involving 500 fighter jets, according to a statement carried by the official KCNA news agency.Five hundred fighters would represents almost every dedicated combat aircraft in the North's inventory, which seems unlikely given many are 40-80 year old airframes and not all are serviceable or kept in the active fleet, said Joseph Dempsey, a defence researcher at the International Institute for Strategic Studies."It's not explicit in their statement, but the design doesn't correspond to one we've seen before," said Ankit Panda, a missile expert at the Carnegie Endowment for International Peace."