(24.Mai 2010) I suspect that the US military had not informed the ROK that an American submarine was stationed underwater near Byaengnyeong Island. If the American submarine that sank at the third buoy was underwater for a long time, it follows that it did not participate in the joint exercise that day (it had other duties).

I think it likely that the US submarine, which was off the coast to the south of Byaengnyeong, happened to approach closer to the shore than expected and ROK forces, mistaking it for a North Korean submarine, fired. When the US submarine returned fire, both boats sank as a result of a friendly attack due to a misconception. The US submarine must have known of the approach of the Cheonan with the use of a passive sonar used for receiving communication. But if the American military was keeping the presence of the submarine secret from the ROK, then the US submarine could not communicate by radio with the Cheonan.