SEOUL—A South Korean has crossed the heavily fortified border in a rare defection to North Korea, South Korea’s military said on Sunday. The Joint Chiefs of Staff (JCS) said it carried out a search operation after detecting the person around 9:20 p.m. (7:20 ET) on Saturday on the eastern side of the Demilitarised Zone (DMZ) separating the two Koreas. “We’ve confirmed that the person crossed the Military Demarcation Line border about 10:40 p.m. (8:40 ET) and defected to the North,” the JCS said. The JCS said it could not confirm whether the person was alive, but sent a notice to the North via a military hotline asking for protection. The border crossing, which is illegal in South Korea, came as North Korea carries out strict anti-coronavirus measures since shutting borders in early 2020, though it has not confirmed any infections. A public and political uproar emerged after North Korean troops …