Sinking of the ROKS Cheonan
Also called: Cheonan incident
The navy corvette Cheonan broke in two and sank off Baengnyeong Island, killing 46 sailors. A joint civilian–military investigation concluded that a North Korean submarine had torpedoed it; North Korea denied it.

Mass Communication Specialist 2nd Class Byron C. Linder · Public domain · Source
At about 9:22 p.m. on 26 March 2010 the 1,200-ton corvette Cheonan, on patrol south-west of Baengnyeong Island, broke in two after an explosion and sank. Of its 104 crew, 58 were rescued and 46 died. Warrant Officer Han Joo-ho of the navy’s underwater demolition team also died during the search for the missing.
On 20 May a joint civilian–military investigation group, including experts from the United States, Britain, Australia and Sweden, announced that a torpedo fired by a small North Korean submarine had exploded beneath the ship. North Korea denied involvement and called the findings a fabrication. On 24 May the government announced the May 24 Measures, halting inter-Korean trade and exchanges except at the Kaesong Industrial Complex. On 9 July the UN Security Council condemned the attack in a presidential statement without naming the attacker.