Question: in 2015 Northern Limit Line was written about a war where?

Context paragraphs:
Kim Hak-soon: Kim Hak-soon (born 1954) is a South Korean film director and screenwriter.  Kim wrote and directed the naval thriller film "Northern Limit Line" (2015) which depicts a real-life naval skirmish with North Korea in June 2002.  It drew more than 6 million viewers 29 days after its release on June 24, 2015, making it one of the top-grossing film in 2015.

Northern Limit Line: The Northern Limit Line or North Limit Line (NLL)-북방한계선(in ROK)- is a disputed maritime demarcation line in the Yellow (West) Sea between the Democratic People's Republic of Korea (DPRK) on the north, and the Republic of Korea (ROK) on the south.  This line of military control acts as the "de facto" maritime boundary between North and South Korea.

Baengnyeongdo: Baengnyeong Island (sometimes spelled Baekryeong; ] ) is a 45.8 km2 , 8.45 km long and 12.56 km wide island in Ongjin County, Incheon, South Korea, located near the Northern Limit Line.  The 1953 Korean Armistice Agreement which ended the Korean War specified that the five islands including Baengnyeong Island would remain under United Nations Command and South Korean control.  This agreement was signed by both the DPRK and the United Nations Command.  Since then, it serves as a maritime demarcation between North and South Korea in the Yellow Sea.  It has a population of approximately 4,329.

Five West Sea Islands: Five West Sea Islands (Korean: 西海五島/서해오도) refers to the five islands in the West Sea (Yellow Sea) administrated by Incheon, South Korea.  They are Yeonpyeong Island, Baengnyeongdo, Daecheongdo, Socheongdo and U Island.  Their positions are much closer to North Korea and their sovereignties are claimed by North Korea, but they are controlled by South Korea since the United Nations forces established the Northern Limit Line (NLL) above the islands in 1953 after the Korean War.

Battle of Daecheong: The Battle of Daecheong was a skirmish between the South Korean and North Korean navies near the Northern Limit Line (NLL) on 10 November 2009 off Daecheong Island.  A patrol boat from the northern Democratic People's Republic of Korea (DPRK) was seriously damaged while the navy of the southern Republic of Korea (ROK) sustained no casualties.

List of border incidents involving North Korea: The following is a list of border incidents involving North and South Korea since the Korean Armistice Agreement of July 27, 1953, ended large scale military action of the Korean War.  Most of these incidents took place near either the Korean Demilitarized Zone or the Northern Limit Line.  This list includes engagements on land, air, and sea, but does not include alleged incursions and terrorist incidents that occurred away from the border.  A total of 3,693 armed North Korean agents have infiltrated into South Korea between 1954 and 1992, with 20% of these occurring between 1967 and 1968.

Bonny Serrano Avenue: Colonel Bonny Serrano Avenue, commonly known simply as Bonny Serrano Avenue (also spelled "Boni Serrano Avenue"), is a major east-west thoroughfare in the Eastern Manila District of Metro Manila, Philippines, running between San Juan City and Quezon City.  It forms the northern limit of San Juan and the southern limit of Quezon City's New Manila and Cubao districts and links the Philippine National Police headquarters in Camp Crame with the Armed Forces of the Philippines headquarters in Camp Aguinaldo.  The avenue, formerly called (and still known locally as) Santolan Road, runs from the border between Greenhills, San Juan and Horseshoe Village, Quezon City in the west to the villages of Libis and Blue Ridge by Quezon City's border with Marikina in the east.  It was named after the decorated Korean War hero, Venancio "Bonny" Serrano.

Socheongdo: Socheongdo or Socheong Island is a small 5 kilometer long and 3 kilometer wide island in Ongjin County, Incheon, South Korea, located in south Daecheong Island, near the Northern Limit Line.  It is situated in the Yellow Sea, lying 200 km northwest of Incheon, 40 km southwest of the mainland of South Hwanghae, North Korea, and 200 km northeast of Shandong Peninsula, China.

Daecheongdo: Daecheong Island is a 12.63 sqkm , 7 km long and 6.3 km wide island in Ongjin County, Incheon, South Korea, near the Northern Limit Line.  The 1953 Korean Armistice Agreement which ended the Korean War specified that the five islands including Daecheong Island would remain under U.N. and South Korea control.  This agreement was signed by both DPRK and United Nations Command.  Since then, it serves as a maritime demarcation between North and South Korea in the Yellow Sea (also called West Sea).

Northern Limit Line (film): Northern Limit Line () is a 2015 South Korean naval thriller film written and directed by Kim Hak-soon, based on the real-life events of the Second Battle of Yeonpyeong.  It stars Kim Mu-yeol, Jin Goo, and Lee Hyun-woo.

Supporting paragraphs: Kim Hak-soon Northern Limit Line (film)
Answer: North Korea