Imperial Japanese Navy Concept of Interceptive Operations.

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Concept of Interceptive Operations


The primary Naval strategy for the Imperial Japanese Navy for about thirty years was the concept of Interceptive Operations. This brief piece is about where it came from, why and what kind of actions were involved.

   This concept of operations begins with Akiyama Kaneyuki, considered the father of modern Japanese naval strategy and a disciple of Alfred Thayer Mahan. He had been a senior staff officer on Admiral Togo's Combined Fleet when it had won the Battle of Tsushima Straits. It was considered an ambush naval strategy.

   Akiyama while he was a devotee of Mahan felt that Mahan's strategy was vague and not applicable to the Pacific and the Japanese hypothetical opponent; the United States. He did not feel that annihilation of the opponent fleet was necessary and probably not practical against such a powerful opponent. He believed that Sun Tsu had said victory could be achieved by "breaking the enemy's will to fight and forcing it quit. This was the starting point- the ambush operation at Tsushima. Akiyama and his colleagues devised a prototype of "interceptive operations". It was refined over its thirty year history and involved lying in wait for the US Fleet, attacking with submarines on its trip across the Pacific, then in the area of the decisive battle, attack at night with cruisers and destroyers.

   The Concept of Interceptive Operations became, in era after the 1922 Washington Naval Treaty, Japans answer to the deadlock that it faced with the 10:10:6 ratio that they had agreed on. Based on the idea that if you square the ratio, then that is the combat ratio that you are facing. In this case, 10:6 become 100:36. That is almost 3:1 which in military circles, means almost certain defeat. So, the IJN had to develop a strategy to reduce that combat ratio. The eventual attack on Pearl Harbor was designed to do just that by sinking four battleships. 

    The submarine operations designed to scout the US Fleet and attack it and the decisive battle which was to be fought near the Bonin Islands about 580 miles SE of Japan. The larger submarines were to be sent to the west coast or Hawaii to ambush ships leaving the ports and attacking ahead of the cruising course of the US Fleet. The Japanese did not have confidence that submarines alone could sufficiently reduce the US Fleet through the use of submarines, so they decided to launch large scale night attacks prior to the decisive battle. These would be conducted by destroyers and cruisers. 

   The Japanese began to train intensively for night attacks. Night attacks were not new to the Imperial Japanese Navy, In both the Sino-Japanese and Russo-Japanese Wars, they used night operations were used extensively, so it wasn't something they had not trained for or did not have attack procedures for. Japanese surface ships were designed around the requirements of Interceptive Operations. They were fast, heavily armed with torpedoes, modest range but with poor habitability. The ships were designed for maximum firepower. The designs were not well balanced with dual purpose heavy guns, ASW sensors and weapons and consequently suffered heavy losses at the beginning of the war. The Guadalcanal operation in 1942 alone saw the loss of eleven destroyers, losses that could never be made up.

    To summarize this first entry, the Concept of Interceptive Operations was developed because of the Japanese Navy's realization that they would be facing a different geographical situation than they had in the past and an entirely different and stronger enemy. After the Naval Treaties, she considered herself behind the eight ball with a 10:10:6 ratio so she developed or expanded the ambush tactics used in previous naval combat. However, over the interwar period, the US Navy moved away from the War Plan Orange and was not planning to move across the Pacific for about 1 to 2 years. The CinC of the Combined Fleet, Admiral Yamamoto realized that the Interceptive Operation was not a workable plan and developed the Pearl Harbor Attack Plan in its place. We can explore in later pieces how the naval ship development was affected by the doctrine of interceptive operations and why the whole concept was probably not workable as they developed. We can explore the effects of the designs for that doctrine in the actual War in the Pacific. We might also explore the usefulness of this concept in games.

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Now let's look at the procurement of Naval weapons by the IJN to implement the Concept of Interceptive Operations. One of problems that all historians have with this subject is the lack of information. As stated in "Kaigun" by Evans and Peattie, "the most critical [issue] is the wholesale destruction of files and documents by the Japanese military services and civilian government in the several days after the Japanese surrender that ended the Pacific War. " This means that we will have to the Naval Mission to Japan in 1946, autobiography's and just good analysis of designs. One of the most important documents was written by the War History Department of the Defense Research Institute of the Japanese Self-Defense Agency between the years 1966 to 1980. It is based on most of the Naval records not destroyed and recreation of logs from ships by the surviving personnel who had actually written the original. We don't know the motivations and arguments behind decisions that were made for construction, naval tactics and combat operational plans. We don't know why a certain technology was adopted and another was dropped. We don't know who argued the hardest, as Kaigun says, for and against a particular naval doctrine. We have to just use good historical analysis and some good guessing.

All right, you are the design bureau for the Imperial Naval General Staff. You are assigned the task of establishing requirements and specifications for the ships and their weapons that will be used for the doctrine of Interceptive Operations. Your first task is to review the operational plan for the interceptive operation. The operation is like a series of concentric circles, the outer being long range submarines near the West Coast of the US and Pearl Harbor. These submarine will scout and report the types of ships, numbers and direction of the ships as they leave Bremerton, San Francisco, Long Beach and San Diego. They will trail these ships to Pearl Harbor attacking when possible to begin to reduce the available ships to the fleet. They will keep in contact with the IJN Fleet headquarters to provide them with detailed reports for assessment of their strategy.

The Japanese would have to have another group of submarines near Pearl Harbor and more stationed in the Marshall Island Group, Carolinas and Marianna's with the surface forces placed to intercept the US Fleet after it leaves Hawaiian Islands and begins to move through the Central Pacific to relieve the Philippines and engage the Imperial Japanese Fleet.

Now, we have to decide on requirements. Long range, surface speed and torpedo load would be a priority for the first group. For a second group, probably the same but reduction in range, speed would be appropriate.  We might want to build more of these medium ranged subs, these would be the main submarine force.   Keep in mind that the Japanese in the early 1920's had a limited dockyard capability and experience. The submarines would be patterned after WW1 German designs, probably available easily. We have to remember that in 1924, the Tokyo earthquake leveled that city and all procurements were put on hold for about two years.

Let's see, for range, we have to examine how far it is the fleet base on the coast that is the greatest distance, that would be San Diego. Its at least 5000 miles to that location. We need to get to that position and return, so that's minimum of 10000 miles at cruising speed. To attack, we will have to increase speed to get in front of the ships, and dive, wait then attack. If the US Fleet cruises at 15 knots, we need 20 knots. So now we have to figure fuel consumption at 20 knots for a specific period of time which will reduce fuel supply. So we need about a 15,000 mile range.

For the torpedo load, if we place four tubes forward and two aft, with two reloads, that's about 16 torpedoes. Keep in mind, there are no forward deployed submarine tenders although we could build a couple of supply subs stationed in the Marshalls to provide reloads. That's possible but budgets might not allow it. We would want to build some medium range and some coastal subs for patrolling the Sea of Japan, Yellow Sea and some of the eastern waterways between the islands in both the north and the south. Again, budgets over the years will dictate how many of each we can actually have.

Over the interwar period, technology changed rapidly. Long range land based aircraft like heavy bombers and patrol planes were developed. SONAR was developed, ships became faster, tactics changed. Carrier aviation was developed. All these developments and many more probably would have reduced the effectiveness of the submarines. We know that in WW2, Japanese submarines accomplished little besides sinking the Wasp and torpedoing the Saratoga twice. Apparently, Yamamoto did not believe in the strategy because he opted to attack Pearl Harbor.

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Let's move on to the destroyers. In the interwar period, due to the Washington Naval Treaty of 1922, the Japanese Navy was at a numerical disadvantage due to restrictions in capital ships. Night attacks by torpedo-equipped units would occur before the battleships would fight the final duel. Destroyers were key to this.

They would be organized in divisions of three to four ships of the same class. Three to four divisions would compose a squadron led by a light cruiser which had the C & C function. The attacks would occur at night supported by heavy cruisers which hopefully would break the screen of US ships and allow the destroyers to get to the battle line, attacking at close range. Training and testing gave the range at about 7000 years according "Japanese Destroyer Captain". They would fire their first load, retire, reload then fire again. Destroyer were designed with quick reloading capability on decks. Torpedoes were designed for long range, with wakeless performance. In WW2 these oxygen powered torpedoes were deadly, especially at Savo Island.

As the design bureau, we have to examine the tactics for the destroyer action and decide what is the best characteristics. The first requirement is seaworthiness because the waters in the Western Pacific and Northern Pacific are very rough. So they would have to move the bridge structure back and raise the forecastle to reduce the impact of heavy seas. The freeboard would have to be higher to improve seakeeping. This would all contribute to raising the CG and that means increased roll. That excess roll would not be advantageous for combat action. To offset that, the beam would have to be increase and so would the length to provide the necessary LtoB for speed. To gain about 35 knots or more, we would need a 10 to 1 LtoB ratio. The last requirement is torpedoes. This parameter depends on how many destroyers you can afford to build and how many torpedoes you want to fire in one salvo plus how many capital ships are targets for you. We could deploy twin launchers, one on each side, and one up forward on the forecastle with reloads. That would be four torpedoes in a salvo on each side. We could improve this by deploying triple launchers on each side and one on the forecastle. This gives us six torpedoes in a salvo on each side.

Basically, we want a destroyer that has A. Good seakeeping ability B. High speed C. Large torpedo load. The ship has to be designed around those three parameters. The deck guns should be at least 4.5 or 5 inch. We should pursue the design of a dual purpose deck gun and put AA weapons on these ships as time progresses and aircraft because more of a menace to us.

The destroyer was probably the most deadly weapon in the IJN arsenal and most used. Due to the emphasis on offensive action, ASW equipment was neglected. These ships were large to be able to carry the torpedo loads with other missions simple not considered important. They suffered very high losses.

[director]

The US Navy calculation was based on a percentage of combat power eroded for each unit of distance moved forward. They calculated they would need a ratio of 100/70 in order to have enough power to defeat Japan in the pivotal battle. Japan evidently agreed, and this was the reason for the treaty fight over Japan's share being 60 rather than 70 or 75%.

It is interesting that Japan calculated they would need to get (as I remember) 15% of damage inflicted on the enemy from torpedo hits, and despite the magnificent performance in the Solomons campaign, they didn't get it. Would they have had better luck against a massed US Pacific Fleet? I think Savo Island and some of those other battles form a good argument for 'Yes', at least once or twice.

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The US Navy calculated that they would lose ten percent of the fleet for every 1000 miles. figuring 3000 miles from the Hawaii, that is about 30% of the fleet. For the Japanese, they felt that Fighting Strength(FS) was approximately equal to Mechanical strength times Efficiency(A, The Extent of Training) times Mental Strength. This accounts for their desire even the battleship numbers to 6 to 6 by attacking Pearl Harbor with the mission objective to sink four battleships.

In the Battle of the Java Sea, the IJN's first opportunity to use their massed torpedo attack, they fired 153 torpedoes with only three hits. Their gunnery was just as bad, with only 4 hits out of 1271 8 in shells fired. During the second naval battle of Guadalcanal, Atago and Takao fire eight torpedoes each at 4000 yards and all missed but their 8-inch gunnery was good, getting 16 hits on South Dakota. There are other incidences where the Japanese destroyers, cruisers and battleships fired increased amounts of shells but did not achieve a good hit rate over 10%, generally it was less than 8%. Using Savo as a guide probably is misleading, because after that they lost the next battle at Cape Esperance while later won the Battle of Tassafaronga. There were thirteen surface battles during the war, the Japanese won 6, we won 4, and 3 were a draw. So, can we draw conclusions? No because we never gamed out torpedoes being used at long range during fleet exercises and a whole host of other variances of the decisive battle, so we started at a disadvantage. After the Solomon's campaign, during which the Japanese light forces were really bled dry, we used scouting and air attacks to attrit the Japanese fleet. Almost interceptive operations in reverse.

In my opinion, based on all that I have read and studied the Japanese Navy had one glaring weakness: they planned for what an opponent would do, not what he could do. This lack of alternatives battle strategies cost them four carrier battles which destroyed their air component of their surface fleet. This deficiency would cost them much in the interceptive operations that they had planned for the US Fleet, had Pearl Harbor not occurred. The poor gunnery by the battlecruisers and heavy cruisers would mean that the initial phase to create a hole through which the destroyer squadrons would sail to attack our battlefleet probably would have failed, costing them valuable ships and men. With no attrition of our escorts, they would not be able to reach the battlefleet and the decisive engagement would most likely have been lost. It wouldn't be until the development of carrier based air and land based air, that another component might be able to make up for that failure, but the lack of armor and protected fuel tanks meant terrible losses, as we saw during the war. Keep in mind, that the enemy always has a say in your plans and no plan survives contact with the enemy. The Japanese never were able to absorb these two precepts, like our commanders did. Another point is that the Japanese never trained as a fleet, to use this concept. The squadrons trained separately, but not together as we did in our Fleet Problems from 1922 to 1940.


On the whole, I feel that the Interceptive Operation, as designed, would have failed.

[director]

Where they could come in close under cover of darkness or bad visibility, Japan got good use from her torpedoes. But firing them at long range, as at Java Sea or Komandorski Islands, wasn;t effective.

I completely agree that the IJN had a massive blind spot with not being able to walk around the map and look at things from the other side.

I don't see any path for Japan to win a war with the US. Perhaps if they had found a way to take on the Dutch and/or British without either declaring war on the US, attacking Pearl Harbor or invading the Philippines. I think the US would have gone to war, but it might have taken a while. So... avoiding war with the US was Japan's best path forward.

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Feb 3, 2016 1:39:07 GMT -6 director said:

Where they could come in close under cover of darkness or bad visibility, Japan got good use from her torpedoes. But firing them at long range, as at Java Sea or Komandorski Islands, wasn;t effective.

I completely agree that the IJN had a massive blind spot with not being able to walk around the map and look at things from the other side.

I don't see any path for Japan to win a war with the US. Perhaps if they had found a way to take on the Dutch and/or British without either declaring war on the US, attacking Pearl Harbor or invading the Philippines. I think the US would have gone to war, but it might have taken a while. So... avoiding war with the US was Japan's best path forward.

In certain situations, close quarters with surprise, in most cases the Japanese did get some good shots, but on the whole their torpedo attacks for all their training and development did not really work that well.

There was a dichotomy between one side of the Japanese that decided that war was the only avenue of escape from the predicament that they found themselves in 1937-1940 time period because of their offensive into China and occupation of Indochina. There was the opposing side, that said they must find a way to avoid war with the US at all costs. We know who won that argument, and who lost: the whole nation or maybe it was time for something like this to change Japan's attitude and outlook.

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Here is the paradox, IMO, about the Concept of Interceptive Operations and Yamamoto's Pearl Harbor operation. He conducted the Pearl Harbor attack, to delay the US Fleet for at least, 6 months or longer before they would begin to move across. In other words, he did not accept the viability of the Interceptive Operation concept or he would not have initiated the Pearl Harbor Attack. If that is true, then why emphasize the destruction of four battleships. Those were the numbers needed to balance the force on force ratio and give the Japanese Navy a chance to win the decisive battle. If you do not believe that that operational plan will work, why attack the battleships. Why not go after just the destroyers, cruisers and possibly the Naval Yard and the fuel tanks which would have been a better, logistical target that would have had far reaching effects on the fleet. They never even attacked the Neosho, the largest fleet oiler in the world, which actually sailed out ahead of Nevada during the attack. These were all better targets. He did not even prioritize on carriers, his staff did that when they designed the attack.


While all of this is true, it must be said that Yamamoto must have had, in his mind that the decisive battle would eventually take place in the Pacific but the question is when and where. He knew as did all Imperial Japanese officers in the Army and Navy, that as time progressed, if the war was not quick, they had no chance to win it. So, you have to force the issue as soon as possible. Pearl Harbor was not a decisive battle, just a raid. Coral Sea was never the decisive battle, the IJN did not even know that the two carriers were in the area. So, we must assume that he had decided to force the issue at the Midway. So, how do you force an opponent to battle especially a naval force that can refuse battle when it wants to. You attack something that you know it has to defend. Ah ha, Midway, the gateway to the Hawaiian Islands was that something. So, the decisive battle was going to come, Yamamoto knew that, but it was up to him to decide when and where. But, battleships had nothing to do with it, his best battleships were 300 miles behind Kido Butai with the bulk of the fleet. So, interceptive operations were not implemented at all, because military technology took a different turn and the whole geostrategic situation had changed for the Japanese. Interesting to explore the results of the Japanese pursuit of the Interceptive Operations.

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I wasn't sure where to put this link, but this thread seemed to be the a good spot for it. nationalinterest.org/blog/buzz/your-history-book-lies-imperial-japan-was-crushed-pearl-harbor-80651

The information in this monograph is correct with 20/20 hindsight. I have read numerous books and they essentially say exactly the same thing. Even some Japanese officers probably knew that this attack was fated, which it was. Anyway I hope you enjoy it. If you want to further discuss the points, lets do it.