During the 1930s there would be more evolution in American War Plans in the Pacific, until it eventually lost the Orange moniker in favor of more all encompassing Rainbow Plans.
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Hello everyone and welcome to History of the Second World War Members Episode 21 - The American Navy Pt. 3 - Orange to Rainbow. Last episode we left off our story of War Plan Orange and the American plans for war with Japan in the beginnings of the 1930s. Of course the 1930s would be a period of great changes both within international relations, but also within the realm of military technologies. As technologies and capabilities continued to develop the plans for war in the Pacific had to be continually re-evaluate. At the same time political developments that seemed to make war more and more likely with each passing year. There was growing resentment in Japan around the fact that Japan had been provided with a lower naval displacement limit in the Washington Naval Treaty. At the second London Naval Conference this resentment would finally result in Japan exiting the conference and the treaty system as a whole. In the United States there was also continued anti-Asian sentiment, which would manifest in political acts like the American Immigration Act of 1924. Back in Asia the fighting would begin, and then continue to rapidly expand throughout the 1930s, which may not have had a direct impact on the planning for War Plan Orange, but certainly increased the likelihood that it would have to be activated. Today, we will track some of the changes in the plan throughout the decade, as it finally landed firmly on a more cautious approach when moving across the Pacific, what that meant for the defense of the Philippines, and then the shift to the island hopping strategy that will be familiar to any student of the Second World War. Finally, we will discuss the creation of the Rainbow plans and how the events in Europe caused changes to plans for a war with Japan.
The early 1930s would be filled with the same arguments that had occupied naval discussions over the previous 2 decades. Precisely how much strength could the American Navy project across the Pacific, and would it be enough to deal with whatever the Japanese could mount in defense. During the early 1930s the balance shifted away from those that believed that the American fleet was capable of making it all the way to Manila during that first movement, and instead the destination of the fleet would shift. After 1933, and for most of the 1930s the destination of the fleet was Truk, and evolution we discussed at some length last episode. However one big, and important for future events, change that would be made in 1933 was the resurrection of the idea of island hopping across the Pacific toward Truk, instead of trying to dit in one hop. Previously the plan had been to try and make it across the Pacific in as few hopes as possible, from the West Coast of the United States, to Hawaii, then to Truk or Manila or Guam or some other western base. One of the reasons that this was finally and decisively shifted to far more island hopping would be the fact that in 1933 the Japanese left the League of Nations, and it started to be clear that they would exit the Naval Treaties in the upcoming years when they had to be renewed. One of the clauses of those treaties was that Japan could not fortify any of the islands that it controlled in the Central Pacific which were part of the Mandate system. But if that restraint was removed, then the islands would be fortified, and if there were fortified islands, which would probably be setup with air fields and strike aircraft, then it was unthinkable that they should be left behind as an American fleet sailed past. As said in War Plan Orange: the US strategy to defeat Japan, 1897-1945 by Edward Miller all of the islands of the central pacific suddenly became mysterious ocean redoubts, which could hold any number of surprises, and they would act as a “deep barrier that could neither be ignored or left to a leisurely mopping up.” One key difference between evaluations at this period in 1933, and then later evolutions which would result in the island bypassing seen during the Pacific War, is that in the early 1930s the ability of the Navy to project air power was much lower than what it would later be, this meant that it would be far more difficult, bordering on impossible, for the Fleet to bring with it enough air strength to nullify all of the Japanese held islands along the way. The only way to do that was to establish island bases, so that more planes could be brought into the theater, and then Japanese air units could be destroyed. The changes in War Plan Orange, and the final death of the quick dash to Manila, would be finalized when the Naval Plans were controlled by Captain Samuel Bryant, Director of the Naval War Plans Division, Admiral William H. Standley, Chief of Naval Operations, and Joseph “Bull” Reeves, the foremost naval air enthusiast. Their evolution of the plan, and a full revocation of the dash to Manila, pushed the conversations happening within the navy to more detailed topics. Instead of disputes that spanned the entire Pacific, the disagreements narrowed and zoomed in to discuss which specific islands should be assaulted, how land, sea, and air resources should work together in an amphibious environment, how should the Fleet use its resources during the island assaults when they were not needed for close support. This would set the stage of the planning that would take place over the next decade, and which would be the precursor to the actual strategy pursued during the Pacific War. This would also be the period when some of the issues that we will be discussed for the rest of the podcast start being looked at, planned for, and debated. How should amphibious landing be launched? Which islands should be selected? What precisely is the best way to use carriers? How tied should fleet assets be the island campaigns? Should the objective of the fleet be to offensively engage the Japanese if possible, or to support the island campaigns? These would be, and would remain open questions that even by the end of the Second World War were in some ways not fully decided. During the 1930s when there were even more unknowns the conclusion was simply: The World Wonders.
As various plans and disagreements were worked out, there would also be a large amount of effort spent on gaining as much information as possible on the islands that might play a role in the campaign. The islands were part of Micronesia and were primarily in three different island changes: the Carolines, Marshalls, and Marianas. The Carolines was the most extensive of the chains, with 55 islands spread out over about two thousand miles. The island chain had been colonized by the Spanish, before being sold to Germany after the Spanish-American War. It would then shift from Germany to Japan after the First World War, with the Paris Peace Conference giving the island chain Mandate status under the stewardship of Japan. From a military perspective the focus of the Carolines was on the Truk Atoll. It could provide one of the finest protected anchorages in the Central Pacific, with the usable harbor space being almost 80 kilometers by 50 kilometers. Truk was a critical piece in many American plans during the 1930s, although it would be greatly deprioritized during the war, being hit heavily by American and later British naval aviation while being bypassed in favor of other targets. North and east of the Carolines were the Marshalls, which contained 5 islands and 29 atolls. Many of these atolls had lagoons that were felt to be very useful to the American Navy, with many of them being quite large and deep. The Marshalls were also much closer to Hawaii and Wake Island which would be used as an American air base. It was believed that it would be in the Marshalls that the first American and Japanese units would come into combat. The third set of central pacific islands were the Marianas. The Marianas stretch northward from Guam towards Japan, and unlike the other islands it is a set of volcanic islands that were not atolls but instead were generally rocky and mountainous. During the Second World War this chain would see the battles of Guam, Tianian, and Saipain, and the campaign to retake them from Japan would include the crucial Battle of the Philippine Sea, also called the Great Marianas Turkey Shoot. However, during the 1930s the Marianas were not seen as important pieces in American Pacific Strategy. American Naval Planners were still focused on launching a campaign to move to the Philippines, and in such a campaign the Marianas would be only marginally useful. This was due primarily to the fact that the islands did not have lagoons or other large fleet basing capabilities. This would not change during the war, however they would be made into ideal bases for B-29s that could launch strategic bombing raids on the Japanese home islands. They were of far less use during the 1930s when all the fleet was trying to do was to establish bases that would allow it to quickly move across the Pacific.
On the topic of the Philippines, as plans for the island hopping campaign solidified, the problem of what to do with the Philippines only grew. The delays that the central Pacific Islands would cause meant that the Philippines could not count on any assistance from the American Navy for months, maybe years. At the same time, as air power grew stronger the security of any Naval base on the islands became a greater concern. By the mid-1930s there were concerns among Naval Planners that even a base in the far south of the islands would not be safe due to the growing air power that Japan was capable of launching against any such base. The thought of putting up a serious defense of Manila was also receding quickly into an impossibility. Instead, by 1936 there was clear recognition within the Navy that whatever troops and resources were in the area surrounding Manila were sacrificial in nature, and all they could do was delay the full take over of the islands by the Japanese invaders. Evaluations from Manila during this time would prove to be quite prophetic in terms of how the campaign would later play out after the Japanese attack. It outlined that the defenders would be forced into the Bataan peninsula, and then the area would be slowly reduced by Japanese attacks, until eventually the remaining defenders were pushed off the mainland altogether and were forced back only onto the island of Corregidor, where with no hope of rescue they would also be finally forced to surrender. In the years immediately before the war there were some plans put forward by the Army to greatly increase the fortifications in and around Manila, but the Navy was firmly against any such strategy, as their island hopping campaign meant that no help would arrive until it was too late, no matter how many supplies and troops were put in place. Later events would prove that, in this case, the Navy was correct in its assessments of the defense outlook of the Philippines. The Japanese would arrive in overwhelming strength, and the defending forces under General MacArthur were quickly in retreat. The Filipino forces, under equipped and under trained would melt away in the face of Japanese attacks. Then the campaign would develop almost exactly as predicted in 1936.
While the Philippines was being written off as a lost cause, firm plans would begin to solidify after 1934 around what exactly the Navy would be doing in the Central Pacific. The first task was to find a nice toll in the Marshalls which could function as the Navy’s forward base. They would make the jump to this atolls from Hawaii as early as a few weeks after hostilities began. Then that base would be setup and used to begin a raiding campaign against other Japanese possessions and bases within range of its aircraft. At the same time the overall push for Truk would begin, with the goal being to constantly push forward, establishing air bases on islands along the way to increase the ability of the Navy to project air power against further Japanese possessions. While much of the specifics of this plan would not be used during the war due to the circumstances that the Americans found themselves in during 1942, the detailed done during this stage of planning would mean that the Navy got a lot of planning time into some of the exact topics that it would need during the later move across the Pacific. Amphibious landings, utilizing naval air power to support landings, what was the criteria that made for a good island to seize, when could a Japanese base be bypassed and left behind, what was needed on the island bases and how should it be transported. Those were just some of the topics that would be discussed at great length during the years before 1934 and 1937. The idea of which Japanese held islands could and should be bypassed would under go many shifts during these years, and it would not be officially adopted until 1937. At that time the plan called for only assaulting the absolute minimum number of islands required for American operations. The rest would be assaulted by American planes to destroy any Japanese aircraft, and then whatever was left on the island would be left behind. However, there was not a full revision of the plan for the Marshalls and Carolines after this decision was made. This meant that the final full version of the plan was written in 1935, when 8 islands were thought to be needed for operations against Truk, a number that may have been reduced if the plan had been heavily revised after 1937 . While this plan was developing there were some known shortcomings of what was trying to be done. One issue was how to prevent the Japanese from just constantly committing more and more air resources into the theater, especially during the period before the Americans had a large number of islands on which to base their own squadrons. There was also the problem of how much naval strength the Navy would have to expose to Japanese attacks just to capture the islands. Exactly how effective air attacks would be against naval targets was not well understood, but it was a fact that a large portion of the American capital ships would be in position around the islands for months. This opened them up to attack, even if the Japanese did not also commit their capital ships to the defense. Whether or not the Japanese battleships and carriers would be used in the Marshalls and Carolines was a debated topic. Some in the Navy felt that the Japanese would not risk these ships so far from home, and even if they wanted to supplying them would be a major challenge. Others believed that through the use of Truk and other supply bases the Japanese could commit these ships if they wanted to, although it was still difficult to know whether or not that would actually happen. The plan to push through the islands was built around the large Japanese ships not appearing, because if they did the combination of the japanese ships and land based air power would be very problematic. There was some effort put into planning for some pre-emptive carrier air strikes against Japanese air bases on the islands, but even in the best care scenarios this might only destroy a quarter of Japanese air power in the area. At the time that this planning was occurring the capabilities and numbers of carrier launched aircraft was MUCH lower than it would be during the war. There was also very strong resistance to tying the carriers down to supporting island operations, with plans for the carriers to be to roaming around quite a bit. This made it challenging for naval planners to come up with a viable way to take strongly defended islands without the presence and use of air based squadrons. This really limited possible target opportunities for the first island that would be taken. Eniwetok was eventually chosen to be that first target, if only because it was within range of long ranger bombers from Wake Island. While many adjustments would be made, the one thing that would remain the same is that it would take months, maybe years for the move across the Pacific to the Philippines, there was just no way around it.
During most of the interwar period the United States Navy and Army worked together when it came to planning for a war in the Pacific. However, as the 1930s came to a close, and as war appeared to be imminent in Europe, and then actually started with the German invasion of Poland, plans for a different kind of war had to be devised. War Plan Orange would be forced to greatly change as the chance of the war being only between the United States and Japan in the Pacific became less likely. Instead of such a scenario, it was seen as an almost certainty that any war in the Pacific would also be matched by war in the Atlantic and in Europe. This introduced a whole host of balancing decisions around where resources should be committed, and which theaters would be given priority. The Army was adamant that if the United States was involved in a war with both Germany and Japan then the Pacific should be a theater for defensive strategies while offensives were launched elsewhere. Instead of moving across the Pacific the Army wanted the Navy to merely establish a defensive perimeter that stretched from Alaska, to Hawaii, and then to Panama. The Navy still favored a Pacific offensive, generally in line with the Orange Plans that it had developed over time. There was a tremendous amount of inertia behind the Orange Plans within the Navy, it had been the focal point of all naval planning for decades by the late 1930s. It had played into ship design, fleet tactical development, training exercises, everything had been built around War Plan Orange. But the Navy could not launch its plans without the cooperation and support of the Army, it was Army troops and army aircraft that would be assaulting and defending the islands along the way. To try and square some of these differences the decision was made to task the Joint Planning Committee with the creation of a new set of plans. In the end it would be five joint plans, which would eventually be called the Rainbow Plans based on the variety of different nations that could be involved. The first, or Rainbow One, was seen as the most dire, and involved a war with multiple different enemies from around the world without any major allies. In such a scenario the plan was based entirely around defending North America to prevent an enemy from gaining bases near to American shores. The second plan involved a war with multiple other powers, but while having major allies, primarily Britain and France. The third plan was basically just a restatement of War Plan Orange, a war with Japan in the Pacific. The fourth plan involved expanding the area defended in the first scenario to include all of North and South America. The fifth involved a war with Germany and Japan, with Britain and France as allies, where priority would be given to Europe and the defeat of Germany, which would be the basis for American strategy during the war. Regardless of the exact scenario involved, the Navy would always advocate for offensive operations in the Pacific. Even with a pull back of Army support, the Navy, instead of pulling back from the offensive, just sought to adjust it to work with the reduced resources. Some of these changes involved slowing the advance down, while others involved shifted its starting point. It would be during this period that the decision would be made to move the main fleet base to Hawaii, which cut down on a large portion of the opening moves of any attack. By making more resources available further west, the Navy was able to preserve the plan of attacking into the Marshalls even with the Army focusing elsewhere. However, beyond that initial move was uncertain. Naval planners were not united in thinking this was a good move, and the caution versus proactivity debate that had at one point been an argument about if the fleet could make it to Manila shifted to being one about whether or not the navy could do anything early in a conflict.
During the summer of 1940 all existing plans were instantly re-evaluated after the quick and decisive defeat of France. France had been in many of the more optimistic plans as a valuable and powerful ally. But that was obviously not going to be the case after June 1940, and so the Joint Planning Committee shifted to the most pessimistic of plans, they took Rainbow Four which planned for a Western Hemisphere defense without the aid of European allies. Then to that situation they assumed that the Germans would be able to capture and use a good portion of the British and French fleets. This demanded that almost all capital ships be moved to the Atlantic to meet such an onslaught, forcing the Pacific squadrons into the most defensive footing possible. This would be the plan that was put in place in late May 1940, and it would be approved by President Roosevelt in August. Of all of the miscalculations, this is almost certainly one of them, although it did not end up having any drastic effects. While the defeat of France and Britain were certainly possible, the idea of the bulk of the Royal Navy being captured while in Europe seems very unlikely. This very defensive posture would be changed in mid-1941, with the American Navy moving back to a slightly more aggressive posture. By the time that this change had been made the Battle of Britain had been won, Washington and London were working closer together than ever before. Then in June 1941 the Soviet Union would also enter the war, although the first few months of its defense against Germany did not exactly inspire confidence. All of these developments caused a new round of optimism which allowed the Navy to get back to its treasured passed time, debating what exactly an attack in the Pacific would look like. But this new round of planning existed firmly inside of Rainbow Five, which placed defeating Germany as the nations number one priority. There were also many new aspects of warfare to be considered, with ample evidence of the power of air power both on land and at sea, as well as new generations of designs coming into all air forces around the world. This put far greater emphasis on some of the American held atolls of the Central Pacific, particularly Wake, Johnston, and Midway. If the Central Pacific offensive, and the jump to the Marshalls would be launched, they would have to be held as staging points for aircraft to protect the American fleet and the American capital ships. Capital ships that would be required for that central pacific thrust, especially those battleships, they were absolutely essential as the backbone of the fleet. If something happened to them, plans would have to really change. But they were the strongest ships in the fleet, and they were well protected in Hawaii at the base at Pearl Harbor, surely nothing would happen to the battleships