Why Islands Still Matter in Asia

The enduring significance of the Pacific 'island chains'

The U.S. Marine Corps (USMC)’s contribution to War Plan Orange has been credited largely to Lieutenant Colonel Earl Hancock “Pete” Ellis, one of its intelligence officers, who distinguished himself as an early theorist of amphibious operations. Ellis contributed most directly through his development of Operational Plan 712, “Advanced Base Operations in Micronesia,” approved as a secret “War Plan” in 1921 by his mentor USMC Commandant Major General John Archer Lejeune. In it, Ellis foresaw the island hopping campaigns of two decades later and offered detailed plans for their successful prosecution by U.S. forces. Today, the USMC maintains that “the actual American campaign for Micronesia diverged from Ellis’ plan only in areas affected by technological advances.”

Ellis’s perspicacity may seem extraordinary, and was only fully recognized in hindsight—in part because of his death in 1923 from alcoholic complications in Palau, one of the Japanese-occupied Caroline Islands which he was attempting to survey covertly. But the strength of his conclusions clearly stems from their grounding in then-unprecedentedly-systematic analysis of the island chains’ geography and potential strategic utility. Ellis devoted particular attention to “the continued occupation of the Marshall, Caroline, and Pelew [Palau] Islands by the Japanese,” which “invests them with a series of emergency bases flanking any line of communications across the Pacific throughout distance of 2300 miles.” Describing these features as “a veritable ‘Cloud’ of islands and reefs” containing “chains of low coral stalls,” he offered what for his era was an exhaustive review of their geomorphology and its implications for the operations that he believed would be necessary to wrest them from Japanese control. To this end, he offered a detailed, hierarchical strategy for American seizure of these “inter-supporting island groups” and establishment of “base facilities for the further pursuance of our operations in areas beyond.” Ellis prioritized in particular the recapturing of Guam, “which it is expected will be strongly held by the enemy as a base.”

During the Pacific War, as Ellis foresaw, the U.S. military itself had to hold the island chains it already controlled, and to penetrate fortified Japanese-held island chains. Admiral Earnest King, for instance, believed that controlling Taiwan “would let the U.S. Navy ‘put the cork in the bottle’ of the South China Sea during World War II, severing Japanese SLOCs and thus Japan’s supply of oil and raw materials.” As Vego’s map below indicates, this American exploitation of theater geometry quite literally shaped the outcome of that epic transoceanic struggle.

Emerging victorious from the Pacific War, U.S. strategists soon turned their attention to the importance of the island chains in the nascent Cold War. It was in this period that the “island chains” concept itself was developed and defined clearly. Washington’s postwar Pacific strategy yielded the earliest explicit mention of an island chains concept we have found: a 1948 Joint Chiefs of Staff study demarcating an American defensive perimeter running from the Aleutian Islands, south through occupied Japan, then through Taiwan and the Philippines.

General Douglas MacArthur played a key role in thinking through the geopolitical significance of the island chains during the early Cold War. As Naval War College scholar Toshi Yoshihara points out, MacArthur argued that the U.S. military should establish a “striking force” stationed along a “U-shaped area embracing the Aleutians, Midway, the former Japanese mandated islands, Clark air base in the Philippines, and above all, Okinawa.” In his “Message on Formosa” of 17 August 1950, MacArthur described Taiwan as “an unsinkable aircraft carrier and submarine tender ideally located to accomplish offensive strategy and at the same time checkmate defensive or counter-offensive operations by friendly forces based on Okinawa and the Philippines.” In his 1951 farewell address to Congress, MacArthur distilled his island chain thinking into its most comprehensive and forceful essence, using it as a unifying theme to inform his final policy recommendations concerning the future of American strategy vis-à-vis the Asia-Pacific. In doing so, he described the U.S. Pacific posture as being quite literally based on the central outward-projecting angle of a bastion-battle line: