Moore, Jeffrey M. Spies for Nimitz: Joint Military Intelligence in the Pacific War.

Moore, Jeffrey M. Spies for Nimitz: Joint Military Intelligence in the Pacific War. Annapolis, Md.: Naval Institute Press, 2004, 336pp. $29.95

Despite its title, this book is not about spies but about what is referred to in today's parlance as "intelligence preparation of the battlefield": a sustained process of research and analysis, based on all source collection efforts, that identifies important aspects of potential combat environments. Intelligence preparation of the battlefield provides planners and commanders with "combat intelligence"--about the terrain, weather conditions, enemy order of battle and dispositions--needed to conduct an upcoming operation. For instance, without knowledge of tidal conditions, currents, the composition and slope of a beach, or the location of underwater obstructions and mines, amphibious operations can be doomed to failure before they begin.

In this history of the performance of U.S. intelligence in the Pacific during World War II, Jeffrey Moore links the intelligence provided to planners by the Joint Intelligence Center Pacific Ocean Area (JICPOA) to the outcome of the major amphibious assaults against Japanese-occupied islands. Intelligence preparation of the battlefield, always important, was of great strategic significance in the "island hopping" campaign undertaken by the United States. Planners had to identify atolls or islets that were lightly defended by the Japanese yet possessed the anchorages, landing strips, and fiat terrain that made them suitable as operating bases for the next stage in the campaign. When intelligence analysts provided accurate pictures of the battlefield, operations generally went smoothly and U.S. casualties were light. When they underestimated enemy strength, failed to warn the assault of strange topographic conditions, or failed to anticipate shifts in enemy strategy, the outcome was a grinding attritional battle that generated high losses.

American intelligence analysts and planners knew very little about the Marshall, Mariana, or Caroline Islands. Of course, many of the atolls and islets targeted in the American march across the Pacific were extraordinarily isolated and had been inhabited mostly by Polynesians before the war. More surprisingly, planners also knew little about American islands that had been seized by the Japanese in the immediate aftermath of Pearl Harbor. Guamanians who had left their home island when the Japanese invaded had to be consulted about topography, road networks, and tidal conditions to support plans for the assault on Guam. The U.S. Navy had supposedly been planning operations against Japan for years; it is hard to explain why so little effort had been made to gather basic information about the Pacific islands.

In assessing JICPOA's performance, Moore identifies a perplexing trend--that U.S. intelligence actually deteriorated as the war progressed. Intelligence performed relatively well against early targets (Kwajalein, Eniwetok, Tinian, and Guam), probably because these atolls were lightly defended by the Japanese and relatively few fortifications had to be identified in the planning of shore bombardment. At the start of the war, the Japanese mostly constructed beach defenses, which were easy to spot by submarine and aerial reconnaissance. There were also some early successes in the exploitation of Japanese material and personnel. Documents that were left behind in Guam by the Japanese Thirty-first Army headquarters were a windfall of information about Japanese defenses across the Pacific. JICPOA, however, lacked the translators and analysts needed to go through these materials quickly, a phenomenon that is referred to today as "information overload." The tempo of the campaign was so fast, and intelligence analysis so slow, that important information often reached commanders after a battle was already joined, by which time information could yield only diminishing returns.

Worse, as the war progressed, the Japanese constructed increasingly sophisticated and well camouflaged fortifications in depth, and the time available for U.S. analysts to survey and identify island defenses decreased. Operations were executed in rapid succession, and JICPOA could no longer keep pace. Intelligence estimates decreased in quantity and accuracy just as Japanese defenses were increasing in strength and lethality. The attitudes of senior U.S. officers also changed, as American materiel superiority began to take its toll on the Japanese. Intelligence preparation of the battlefield took a backseat to maintaining the momentum of the drive across the Pacific. Commanders were more interested in bringing the overwhelming weight of U.S. naval, Marine, and army units quickly to bear against the Japanese so that the ghastly attritional campaign might end as soon as possible. As Moore notes, the island campaigns were brought to an end not by brilliant maneuver but by the virtual annihilation of Japanese garrisons.

Moore looks on the bright side of JICPOA's modest performance, but he finds only one outstanding success by its analysts during the war. Ironically, it was in support of an amphibious operation that never occurred, the planned invasion of Kyushu in the autumn of 1945. Because Japanese garrisons usually fought to the death and inflicted high casualties on attacking forces, the five hundred thousand defenders of Kyushu were capable of turning the opening phase of the attack on the home islands into a bloodbath. JICPOA's accurate estimates of the steady buildup of Japanese forces on the island led military planners to support a less costly way to end the war in the Pacific--the use of the atomic bomb against Hiroshima and Nagasaki in August 1945.

JAMES J. WIRTZ

Naval Postgraduate School