On Wednesday morning, North Korea fired more than 10 missiles, including one that landed close to South Korea's waters. South Korean President Yoon Suk-yeol called it "effectively a territorial invasion". One short-range ballistic missile crossed the Northern Limit Line, the de facto maritime border between the two countries, prompting a rare air raid warning for residents on the Ulleungdo island to take shelter in bunkers. Watch this video to learn more.