Answer the following question: Extract the answer to the question from the following context. Question: What happened before the last naval battle took place? Context: Because neither Korea had a significant navy, the Korean War featured few naval battles. A skirmish between North Korea and the UN Command occurred on 2 July 1950; the U.S. Navy cruiser USS Juneau, the Royal Navy cruiser HMS Jamaica, and the frigate HMS Black Swan fought four North Korean torpedo boats and two mortar gunboats, and sank them. USS Juneau later sank several ammunition ships that had been present. The last sea battle of the Korean War occurred at Inchon, days before the Battle of Incheon; the ROK ship PC-703 sank a North Korean mine layer in the Battle of Haeju Island, near Inchon. Three other supply ships were sunk by PC-703 two days later in the Yellow Sea. Thereafter, vessels from the UN nations held undisputed control of the sea about Korea. The gun ships were used in shore bombardment, while the aircraft carriers provided air support to the ground forces.
Answer:
the ROK ship PC-703 sank a North Korean mine layer in the Battle of Haeju Island