North Korea continued its series of missile tests this week, for the first time firing a ballistic weapon over Japan. Residents of Hokkaido island received text messages urging them to seek shelter in “a sturdy building or basement”. Many analysts see Pyongyang’s latest missile test as one of the most provocative yet. Japanese Prime Minister Shinzo Abe said North Korea’s “reckless action is an unprecedented, serious and a grave threat to our nation”. Jointly with South Korea he has pushed for tougher sanctions against Pyongyang in the UN Security Council. Reuters reported that Tokyo was seeking a powerful radar system known as Spy-6 from the US, but efforts to secure it have so far come to naught. Washington’s reluctance to provide the system could play into the hands of North Korea, which is hoping to sow divisions between the two allies.