Island Chain Strategy

The Island Chain Strategy is a plan first conceived by American foreign policy commentator John Foster Dulles in 1951 during the Korean War. It proposed surrounding the Soviet Union and the People's Republic of China by sea. The island chain concept did not become a major theme in US foreign policy, but has remained a major fixation of both American and Chinese political and military analysts to this day. For the United States, the island chain strategy is a significant part of the force projection of the U.S. military in the eastern part of Asia. For China, the concept is integral to its fears of encirclement by U.S. armed forces. For both sides, the island chain strategy emphasizes the geographical and strategic importance of Taiwan.
First Island Chain.
The First Island Chain is defined as the chain of islands that begins at the Kuril Islands, runs through the Japanese Archipelago, the Ryukyu Islands and Taiwan, the northern portion of the Philippines, and finishes towards Borneo. It was conceptualized as the first chain of defence to contain the spread of influence of the Soviet Union and alligned socialist countries in East Asia and the Pacific. The key part of the first chain was––and still is––Taiwan.
Because the island chain is composed of a series of landmasses, it is also called the "unsinkable aircraft carrier", especially in reference to Taiwan.
Second Island Chain.
The Second Island Chain can refer to two different interpretations, but the version most commonly used refers to the island chain which is formed by the Bonin Islands and Volcano Islands of Japan, in addition to the Mariana Islands, most notably Guam, which is United States territory.
As it is located within the middle portion of the Pacific Ocean, it acts as a second strategic defense line for the United States.
Third Island Chain.
The Third Island Chain is the final part of the strategy. This island chain begins at the Aleutian Islands and runs through Oceania in the central Pacific. The Hawaiian Islands are included in this chain.
Fourth and fifth island chains.
The Asia Maritime Transparency Initiative argues that a fourth and fifth island chain should be added to an overall understanding of Chinese maritime strategy. Whereas the first three island chains are located in the Pacific Ocean, these two newly proposed ones are in the Indian Ocean, which would reflect the growing Chinese interest in the region. The fourth island chain would include places like Gwadar, Hambantota and Diego Garcia, while the fifth island chain would originate from China's naval base at Doraleh, Djibouti.
Target and events.
The primary target of the doctrine was the USSR; however, additional targets also included the People's Republic of China, Vietnam, and North Korea. After the collapse of the USSR in 1991, China became the major target of the doctrine.