Kim Jong-un launched another missile into the Sea of Japan early Friday morning and flew warplanes along its border with South Korea, adding to the rounds of weapon tests conducted by the volatile nation since late September. The authoritarian state, which described the tests as simulated nuclear attacks on South Korean and U.S. targets, said it was acting in retaliation against South Korea’s mobilization, accusing it of practicing artillery fire for 10 hours along the countries’ shared border on Thursday. It also blamed its “strong military countermeasures” on the return of a U.S. aircraft carrier to the Korean peninsula, which began practicing naval drills on Oct. 6. The USS Ronald Reagan arrived to the region after North Korea fired its first missile in the direction of Japan, hours after Vice President Kamala Harris left the demilitarized zone between the North and the South. North Korea has conducted the record-breaking series of tests in a vie to be viewed as a nuclear power and break U.N. economic sanctions against the Kim regime.