Japan sent an Aegis destroyers to the Sea of Japan, in the area North Korea is using for short range missile tests. Aegis is the top-line American anti-aircraft and anti-missile radar technology that equips many Japanese warships.
The US has sent six F-117 stealth aircraft to South Korea for training exercises later this month. If the North Koreans were paranoid before, this is not going to help calm them down. F-117s are used to launch attacks on aid defense systems. While six F-117s could not put a large dent in the North Korean air defenses, North Korean fears are based more on symbols than facts and the F-117's arrival will be denounced as another "provocation".