The South Korean Navy corvette Cheonan sank off the coast of Baengnyeong Island in the Yellow Sea, killing 46 of the 104 crew members onboard. The ship was conducting a routine patrol when it was struck by an underwater explosion, which was later determined to be caused by a torpedo. Following the incident, an international investigation was launched, with the involvement of experts from the United States, Australia, Britain, and Sweden. The results indicated that a North Korean submarine was responsible for the attack. As a result, the United Nations Security Council convened to discuss the implications of the incident.

On May 20, 2010, the President of the United Nations Security Council publicly stated that North Korea was to blame for the sinking of the Cheonan. The incident not only escalated military tensions between South Korea and North Korea but also raised concerns regarding regional security and the international community’s response to North Korean aggression. The South Korean government imposed sanctions on the North and conducted military exercises, further straining bilateral relations. The Cheonan incident became a focal point for discussions on North Korea's naval capabilities and the broader implications of its actions within the context of international law and regional stability.

The sinking of the Cheonan also had lasting impacts on South Korea's defense posture and military strategy. In the wake of the attack, South Korea took measures to strengthen its military readiness and enhance the capabilities of its naval forces, reflecting a shift towards a more proactive defense strategy. Furthermore, the incident prompted discussions within the global community regarding the need for more stringent policies and sanctions against North Korea to deter its aggressive military actions and uphold international peace and security.