Yellow Sea in the context of "Marginal sea"

The East China Sea is a marginal sea of the Western Pacific Ocean, located directly offshore from East China. China names the body of water along its eastern coast as "East Sea" (Dōng Hǎi, simplified Chinese: 东海; traditional Chinese: 東海) due to direction, the name of "East China Sea" is otherwise designated as a formal name by International Hydrographic Organization (IHO) and used internationally.

It covers an area of roughly 1,249,000 square kilometers (482,000 sq mi). The sea's northern extension between Korean Peninsula and mainland China is the Yellow Sea, separated by an imaginary line between the southwestern tip of South Korea's Jeju Island and the eastern tip of Qidong at the Yangtze River estuary.

North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korean Peninsula and borders China and Russia to the north at the Yalu (Amnok) and Tumen rivers, and South Korea to the south at the Korean Demilitarized Zone (DMZ). The country's western border is formed by the Yellow Sea, while its eastern border is defined by the Sea of Japan. North Korea, like South Korea, claims to be the sole legitimate government of the Korean Peninsula and adjacent islands. Pyongyang is the capital and largest city.

The Korean Peninsula was first inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early 7th century BCE. Following the unification of the Three Kingdoms of Korea into Silla and Balhae in the late 7th century, Korea was ruled by the Goryeo dynasty (918–1392) and the Joseon dynasty (1392–1897). The succeeding Korean Empire (1897–1910) was annexed in 1910 into the Empire of Japan. In 1945, after the Japanese surrender at the end of World War II, Korea was divided into two zones along the 38th parallel, with the north occupied by the Soviet Union and the south occupied by the United States. In 1948, separate governments were formed in Korea: the socialist and Soviet-aligned Democratic People's Republic of Korea in the north, and the capitalist, Western-aligned Republic of Korea in the south. The North Korean invasion of South Korea in 1950 started the Korean War. In 1953, the Korean Armistice Agreement brought about a ceasefire and established a demilitarized zone (DMZ), but no formal peace treaty has ever been signed. Post-war North Korea benefited greatly from economic aid and expertise provided by other Eastern Bloc countries. However, Kim Il Sung, North Korea's first leader, promoted his personal philosophy of Juche as the state ideology. Pyongyang's international isolation sharply accelerated from the 1980s onwards as the Cold War came to an end. The fall of the Soviet Union in 1991 then brought about a sharp decline to the North Korean economy. From 1994 to 1998, North Korea suffered a famine with the population continuing to suffer from malnutrition. In 2024, the DPRK formally abandoned efforts to reunify Korea.

South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and the Sea of Japan to the east. Like North Korea, South Korea claims to be the sole legitimate government of the entire peninsula and adjacent islands. It has a population of about 52 million, of which half live in the Seoul metropolitan area, the ninth most populous metropolitan area in the world; other major cities include Busan, Daegu, and Incheon.

The Korean Peninsula was inhabited as early as the Lower Paleolithic period. Its first kingdom was noted in Chinese records in the early seventh century BC. From the mid first century BC, various polities consolidated into the rival kingdoms of Goguryeo, Baekje, and Silla. The lattermost eventually unified most of the peninsula for the first time in the late seventh century AD, while Balhae succeeded Goguryeo in the north. The Goryeo dynasty (918–1392) achieved lasting unification and established the basis for the modern Korean identity. The subsequent Joseon dynasty (1392–1897) generated cultural, economic, and scientific achievements and also established isolationism starting from the mid-17th century. The succeeding Korean Empire (1897–1910) sought modernization and reform but was annexed in 1910 into the Empire of Japan. Japanese rule ended following Japan's surrender in World War II, after which Korea was divided into two zones: the Soviet-occupied northern zone and the United States-occupied southern zone. After negotiations on reunification failed, the southern zone became the Republic of Korea in August 1948, while the northern zone became the communist Democratic People's Republic of Korea the following month.

Northeast China (Chinese: 东北; pinyin: Dōngběi) is a geographical region of China, consisting officially of three provinces Liaoning, Jilin and Heilongjiang. The heartland of the region is the Northeast China Plain, the largest plain in China with an area of over 350,000 km (140,000 sq mi). The region is separated from the Russian Far East to the north and east by the Amur, Argun and Ussuri Rivers; from North Korea to the south by the Yalu and Tumen Rivers; and from the neighboring North China to the west by the Greater Khingan Range and Yan Mountains. It is also bounded by the Bohai Bay and Yellow Sea to the southwest, about 100 km (62 mi) away from East China's Jiaodong Peninsula across the Bohai Strait, due to be connected via a proposed undersea tunnel.

The four prefectures of Inner Mongolia (which is part of North China) east of the Greater Khingan, i.e. Chifeng, Tongliao, Hinggan and Hulunbuir, are sometimes also considered broader parts of Northeast China, and together with the aforementioned three provinces formed what was historically known as Inner Manchuria, in contrast to the Outer Manchuria (or "Outer Northeast" in Chinese literatures) annexed by the Russian Empire during the mid-19th century.

Jiangsu is a coastal province in East China. It is one of the leading provinces in finance, education, technology, and tourism, with its capital in Nanjing. Jiangsu is the third smallest, but the fourth most populous, with a population of 84.75 million, and the most densely populated of the 22 provinces of the People's Republic of China. Jiangsu has the highest GDP per capita and second-highest GDP of Chinese provinces, after Guangdong. Jiangsu borders Shandong in the north, Anhui to the west, and Zhejiang and Shanghai to the south. Jiangsu has a coastline of over 1,000 kilometers (620 mi) along the Yellow Sea, and the Yangtze flows through the southern part of the province.

Since the Sui and Tang dynasties, Jiangsu has been a national economic and commercial center, partly due to the construction of the Grand Canal. Cities such as Nanjing, Suzhou, Wuxi, Changzhou, and Shanghai (separated from Jiangsu in 1927) are all major Chinese economic hubs. Since the initiation of economic reforms in 1990, Jiangsu has become a focal point for economic development. It is widely regarded as one of China's most developed provinces, when measured by its Human Development Index (HDI). Its 2021 nominal GDP per capita reached CN¥137,300 (US$21,287), becoming the first province in China to reach the $20,000 mark.

The North China Plain (simplified Chinese: 华北平原; traditional Chinese: 華北平原; pinyin: Huáběi Píngyuán) is a large-scale downfaulted rift basin formed in the late Paleogene and Neogene and then modified by the deposits of the Yellow River. It is the largest alluvial plain of China. The plain is bordered to the north by the Yanshan Mountains, to the west by the Taihang Mountains, to the south by the Dabie Mountains, and to the east by the Yellow Sea and Bohai Sea. The Yellow River flows through the plain, before its waters empty into the Bohai Sea.

The part of the North China Plain around the banks of the middle and lower Yellow River is commonly referred to as the Central Plain (pinyin: Zhōngyuán). This portion of the North China Plain formed the cradle of Chinese civilization, and is the region from which the Han Chinese people emerged.

The Bohai Sea (Chinese: 渤海; pinyin: Bó Hǎi; lit. 'Bo Sea') is a gulf/inland sea approximately 77,000 km (30,000 sq mi) in area on the east coast of Mainland China. It is the northwestern and innermost extension of the Yellow Sea, to which it connects via the Bohai Strait. It has a mean depth of approximately 18 meters (59 ft), with a maximum depth of about 80 meters (260 ft) located in the northern part of the Bohai Strait.

The Bohai Sea is enclosed by three provinces and one direct-administered municipality from three different regions of China—Liaoning Province (of Northeast China), Hebei Province and Tianjin Municipality (of North China), and Shandong Province (of East China). It is the center of the Bohai Economic Rim, and its proximity to the Chinese capital of Beijing and the municipality of Tianjin makes it one of the busiest seaways in the world. The entrance to the Bohai Sea is considered a part of the territorial sea of the People's Republic of China due to the presence of the Miaodao islands. China declared the Bohai sea to be part of its inland waters in 1958.

Ganghwa Island (Korean: 강화도), also Ganghwado, is an island in Ganghwa County, Incheon, South Korea. It is in the Yellow Sea and in an estuary of the Han River.

The island is separated from Gimpo (on the South Korean mainland) by a narrow channel spanned by two bridges, and from Kaesong (Gaeseong) in North Korea by the main channel of the Han River. It offers some of the closest views in the South of North Korean villages, which can be seen on clear days from less than two kilometers.

The Russo-Japanese War (8 February 1904 – 5 September 1905) was fought between the Russian Empire and the Empire of Japan over rival imperial ambitions in Manchuria and the Korean Empire. The major land battles of the war were fought on the Liaodong Peninsula and near Mukden in Southern Manchuria, with naval battles taking place in the Yellow Sea and the Sea of Japan.

Russia had pursued an expansionist policy in Siberia and the Far East since the reign of Ivan the Terrible in the 16th century. At the end of the First Sino-Japanese War, the Treaty of Shimonoseki of 1895 had ceded the Liaodong Peninsula and Port Arthur to Japan before the Triple Intervention, in which Russia, Germany, and France forced Japan to relinquish its claim. Japan feared that Russia would impede its plans to establish a sphere of influence in mainland Asia, especially as Russia built the Trans-Siberian Railroad, began making inroads in Korea, and acquired a lease of the Liaodong Peninsula and Port Arthur from China in 1898. Japan signed the Anglo-Japanese Alliance in 1902, and began offering to recognize Russia's dominance in Manchuria in exchange for recognition of Korea as part of Japan's sphere of influence. However, this was rejected by Russia.