North Korea’s military said Monday that missile tests last week were preparation for striking South Korean and U.S. military targets. The military also said the tests were an answer to large U.S. and South Korean air force drills. This year’s drills involving the U.S. and South Korea were the largest ever for their annual fall exercises. The drills involved 240 warplanes including high-technology F-35 fighter jets. The allies had planned to carry out drills for five days ending on Friday. But South Korea and the U.S. held an additional day of training in reaction to the North’s missile tests. The General Staff of North Korea’s military said in a statement that the North will answer U.S. and South Korean military exercises with more of its own exercises. North Korea launched more than 20 missiles and flew warplanes towards its sea border last week. Those actions caused evacuation warnings in some areas of South Korea and Japan. North Korea said some cruise missiles fell in international waters about 80 kilometers from South Korea’s southeastern coastal city of Ulsan. The North’s military said it also tested a ballistic missile with a special warhead with the goal of “paralyzing the operation command system of the enemy.” Some observers suggest the statement could describe an attack using electromagnetic energy. But it is unclear whether North Korea has developed such technology or can use it.