|Japanese operations against the Australian mainland in the Second World War:
A survey of Japanese historical sources
The war in the Pacific theater of the Second World War, which started in December 1941 with major operations by the Japanese against Hawaii, Malaya and the Philippines, quickly worked its way into the south-west Pacific area, reaching the Australian mainland in February 1942 in the form of a massive air raid on Port Darwin. For nearly two years after that, the Japanese continued their attacks by air on Port Darwin and other towns on the northern and western coasts of the Australian mainland, and also carried out a few attacks by submarine, most notably at Sydney. While these operations were much smaller in scale than the battles and campaigns fought in the Solomons–New Guinea area and the central Pacific during that period, they are an important aspect of the war fought between Japan and the Allies.
The following essay is a survey of the existing Japanese-language source materials relating to Japanese operations against the Australian mainland during the Second World War. It should be noted that it does not cover operations by the Japanese in New Guinea and the Solomon Islands, which could administratively be considered part of Australia at the time In fact, the Japanese often referred to the New Guinea – Solomons area as “Northern Australia” (Gôhoku). This can sometimes be misleading; e.g. a file labeled, for example, “Operations in North Australia” often contains documents relating only to operations in the New Guinea – Solomons area. It should also be noted that the records are incomplete. Many documents of a purely military nature were destroyed by the Japanese at the end of the war to keep them from falling into enemy hands; others were lost during the war, or at the war’s end in the general confusion of defeat. Fortunately, however, much has survived. In the case of the documents discussed here, some records have been completely preserved and have been extremely useful for studying Japanese operations against the Australian mainland.
Overview of Japanese attacks on the Australian mainland 
The Japanese operations against Australia consisted primarily of bombing and strafing attacks by land-based bombers and fighters of the Imperial Japanese Navy. These began with a major attack on Port Darwin on 19 February 1942 and continued through November 1943. While a number of these attacks were made by twenty or more aircraft, in most cases the attacking force consisted of less than ten planes. Japanese carrier-based aircraft were involved only once, when 188 planes of the Mobile Fleet (Kidô Butai, including aircraft carriers Akagi, Kaga, Hiryû and Sôryû) took part in that initial raid on 19 February 1942. Although its reconnaissance aircraft flew numerous missions over Australia, aircraft of the Imperial Japanese Army took part in only two attacks, which occurred in late-June 1943.
The primary air units involved in these operations were as follows. The bulk of the missions from March 1942 onwards were flown by bombers of the Takao Air Corps (Takao Kôkûtai) and fighters of the 3rd Air Corps (Dai 3 Kôkûtai). These were renamed the 753rd and 202nd Air Corps respectively, in a major reorganization of the Japanese Naval Air Force which became effective 1 November 1942. Both of these were land-based units operating out of Kendari and Kupang in the Dutch East Indies. Other land-based naval air units which were involved were the Tainan Air Corps (Tainan Kôkûtai; fighters) and 4th Air Corps (Dai 4 Kôkûtai; bombers), which flew several missions out of Rabaul and Lae during the spring and summer of 1942, primarily against Horn Island, until the battle of Guadalcanal required their full attention from early August 1942. Bombers of the 1st and Kanoya Air Corps (Dai 1 Kôkûtai and Kanoya Kôkûtai), based in Ambon and Kendari respectively, flew in the initial February 1942 raid, but were not involved in any of the later operations.
As mentioned above, carrier-based planes took part only in the February 1942 raid on Port Darwin. These were planes from the aircraft carriers Akagi and Kaga, which comprised the 1st Carrier Division (Dai 1 Kôkûsentai), and the Hiryû and Sôryû, which comprised the 2nd Carrier Division (Dai 2 Kôkûsentai).
Compared with these naval air forces, the Japanese Army air forces played a relatively minor role in Japanese operations against Australia. Bombers and fighters of the 3rd Air Brigade (Dai 3 Hikôdan), 7th Air Division (Dai 7 Kôkû Shidan) and 3rd Air Army (Dai 3 Kôkûgun) participated in the only air raids by Army planes on Australia, which occurred on 20 and 22 June 1943 from Lautem in the East Indies. The bombers were from the 61st and 75th Air Regiments (Hikô Dai 61 Sentai and Hikô Dai 75 Sentai, respectively), while the fighters were from the 59th Air Regiment (Hikô Dai 59 Sentai). Reconnaissance aircraft of the 70th Independent Air Company (Dokuritsu Hikô Dai 70 Chûtai; also under the 3rd Air Brigade), however, did fly numerous scouting missions over Australia before and after these air raids.
Finally, submarines were also involved in Japanese operations against Australia. The most famous action was the attack by midget submarines in Sydney Harbour on 31 May 1942. Submarines also bombarded coastal targets in the Port Gregory area with their deck guns in January and February 1943, and also carried out a minor minelaying operation off Brisbane in March 1943. Merchant raiding missions and patrols were also naturally carried out at various times during the war off the coast of Australia, but these were not included in the scope of this paper.
The submarines that operated against Australia were I-class boats. I-25 of the 4th Submarine Squadron (Dai 4 Sensuitai) conducted scouting missions against Sydney, Melbourne and Hobart in February and March 1942. I-29 of the 14th Submarine Squadron (Dai 14 Sensuitai) took part in the mission against Sydney in May 1942. I-21 of the 3rd Submarine Squadron (Dai 3 Sensuitai) carried out missions against Sydney in May 1942, which involved the launching of the midget submarines mentioned above, and in January 1943. I-6 was the submarine involved in the Brisbane minelaying operation, while the shore bombardments were conducted by I-165 of the 30th Submarine Squadron (Dai 30 Sensuitai).
Location of Sources
All of the primary sources may be found in the military history archives of the library of the National Institute for Defense Studies (Bôei Kenkyûjô), the research institution of the Japan Defense Agency (Bôeichô). This is located in Tokyo and is open to the public. This fortunate situation for the scholar came to be because all of the existing official papers of the Imperial Japanese Navy and Army were assembled by the War History Office (Senshishitsu) of the institute’s predecessor, the National Defense College (Bôei Kenshushô), when it compiled and published Japan’s 102-volume official history of the Second World War in the 1970s and 1980s. Some other official documents of the Navy may be found at the Shôwakan in Tokyo, but as far as source materials concerning Japanese attacks on Australia are concerned, the only materials there which may be relevant are the orders and directives of the highest level in the Navy; copies of nearly all of these have been deposited in the National Institute’s library, however, or have been reprinted in the official history Unless otherwise noted, therefore, all of the primary sources referred to in this paper are in the possession of the library of the National Institute for Defense Studies.
It should be noted that most if not all of the primary documents are in handwritten Japanese and, in some cases, might be difficult to read. While many of the documents are in very good condition, some are faded and nearly illegible. Most are available on microfilm.
Primary sources: Naval air units
By far the best and most impressive set of primary sources concerning the Japanese operations against Australia are the action reports (kôdô chôsho) of the naval air units involved. The action reports of the 1st, Kanoya, Takao and 3rd Air Corps from December 1941 through October 1942 are complete, as well as those of the 753rd Air Corps from November 1942 through July 1944 and the 202nd Air Corps from November 1942 through October 1943. In addition, the action reports of the air units on the aircraft carriers Akagi, Hiryû and Sôryû, which took part in the initial 19 February 1942 raid on Port Darwin, have also survived; the reports of the Kaga are missing, however. These contain the daily action reports of each air corps in great detail, listing in a series of tables the action which occurred (e.g. reconnaissance, aerial combat, bombing); date; mission; commander; number of each type of plane (e.g. fighter, bomber, scout) taking part; ordinance carried; results (e.g. shot down, forced landing, types of targets bombed); timeline for each mission, including the bases flown from, times of departure and return; the times certain objectives were flown over or actions occurred; and damage and casualties incurred. In addition, the name and rank of each pilot and aircrew involved, the formations of the flights, and the fate of each aircrew (such as killed in action, wounded, or missing) are given in a separate table. While these reports are also handwritten in Japanese, they fortunately are quite legible. The action report for each day was written up at the end of the day, except in a few cases where the original was lost and had to be recreated later, usually from memory. These are all on microfilm, and every mission flown by naval aircraft against Australia through the fall of 1943, when such attacks ceased, may be reconstructed in nearly every detail by using these records. As is the case with any such records, however, it is probably preferable to check the results of the aerial combat or bombing reported therein with Australia records for greater accuracy.
Continuing with operations of the naval air units, the records for the next higher level of command – the air flotillas – unfortunately are incomplete. The war diaries (senji nisshi) and battle reports (sento shôhô) of the 1st Mobile Fleet, which included the four aircraft carriers that attacked Port Darwin in February 1942, as well as those of the 21st Air Flotilla, which commanded the Kanoya Air Corps, are missing. The diaries and reports of the 23rd Air Flotilla, which commanded the Takao and 3rd Air Corps, and later the 753rd and 202nd Air Corps, are available only from April 1944 onward, which is after it ceased operations against Australia. The war diaries of the 24th Air Flotilla, under which the 1st Air Corps operated, are available from February 1942 through to the end of the year, and then from March 1943 onwards. The diaries of the 25th Air Flotilla, which included the Tainan and 4th Air Corps, are also available for the period from March 1942–May 1944, which naturally includes the period (March–July 1942) during which these units bombed Horn Island a number of times. The entries in all of these diaries and battle reports, however, consist primarily of weather reports and the fact that certain types of planes flew a mission, along with brief comments on the results. For example, a notation might read, “Type 1 Bombers [Betty] attacked Horn Island but had to turn back because of the weather.” These diaries and reports are therefore useful for determining dates and missions of operations over Australia, but not much more in terms of detail. Most are available on microfilm, but in general are not as clear and easy to read as the action reports mentioned above.
The records of the next higher levels of command – the Air Fleets and Combined Fleet – may be found at the Shôwakan, while copies made from these have been deposited in the National Institute’s library. Since most of the relevant orders and directives have been reprinted in the official war history mentioned above, it would probably be sufficient to refer to these histories for the contents of higher-level orders and directives, especially since they are much more legible Atene Shobo has recently published an 18-volume set containing reprints (actually, copies) of the battle reports of nearly every unit in the Imperial Japanese Navy, from the Naval General Staff down to individual ships and air corps. Unfortunately, many of the reports of the lower level units had to be abridged, and cover only certain periods; the reports of the Australian operations of the units that took part in them may therefore not all be contained therein.
Primary sources: Army air units
While, as mentioned above, source materials for the naval air units involved in operations against Australia are fairly complete and provide many details, especially at the level of the front-line units, the same does not hold true for the relevant Army air units. It appears that none of the war diaries of the three air regiments involved – the 59th, 61st and 75th Air Regiments – have survived for June 1943, which was when they made their two attacks in the Darwin area. In fact, the official histories for these actions were based mainly on recollections of the participants. A short history of the 70th Independent Air Company was written shortly after the war in the form of a timetable. Unfortunately, all it mentions are the missions undertaken by certain units; thus, it is possible to determine that the 70th Company flew a reconnaissance mission over the Darwin area as late as November 1944, but not much more. Interestingly, some of the naval records given above for June 1943 mention that the missions were flown together with Army air units and thus, are useful in determining the actions of these Army units. But again, details other than the date, targets and units involved are not available.
Primary sources: Submarines
Primary sources concerning Japanese submarine operations against Australia are also, unfortunately, quite limited. The only surviving war diaries of the submarines which operated against Australia are those of the I-21, which participated in the midget submarine attack in Sydney Harbour on 31 May 1942. The war diaries are handwritten and relatively legible, but are not yet available on microfilm. They consist of reports for a certain month, or period of months, in which details of the unit’s missions, personnel assignments, orders received and given, and surveys conducted, among other activities, are recorded. A day-by-day timeline recording the daily activities of the unit is also included, as well as various technical information, such as fuel usage or the condition of power plants. Since the timeline is written with a fair amount of detail, including, for example, weather reports and a brief time log for each day, it is probably the most useful section for historians. But other sections, such as the orders given and received, would also be useful given the relative unavailability of other primary sources for submarines. It should be noted that pages are missing here and there throughout the diaries.
The other major primary source material for submarines are the combat reports (sento shôhô) of the 6th Fleet (Dai 6 Kantai), which commanded the various submarine divisions and squadrons of the other submarines which conducted reconnaissance missions over Australia with their floatplanes, or bombarded Port Gregory in January–February 1943 with their deck guns. These contain a fair amount of detail concerning the activities of the individual submarines under the 6th Fleet’s control. In the absence of the war diaries or combat reports of submarines other than the I-21, the 6th Fleet diaries are the only primary source for the operations of these other submarines. These are not yet available on microfilm.
Secondary literature: the official war history
The secondary source that must be read by anyone researching Japanese operations in the Second World War, including those against Australia, is the 102-volume Senshi Sôsho. The War History Office of the National Defense College compiled this, as noted above, and published it from 1966 through 1980. It is currently available only in Japanese, although attempts are being made to translate portions of it into English. It is also currently out of print. Since virtually all of the surviving official records of the Imperial Army and Navy were assembled by the War History Office specifically for this project in the 1960s, and since these were used extensively, together with personal diaries and recollections when compiling the history, it by itself is quite useful to many researchers. In addition, as also noted above, many higher-level orders and directives have been reprinted in full in the relevant sections of the history, enabling the reader to view them without searching for the original document. One of the official history’s major drawbacks is its immensity; it is quite easy to get lost in its details and grasping the overall picture may be difficult. Another problem with the history arises from the fact that it was published in the order that the individual volumes were completed, and not in chronological order, which can make it exasperating to find the relevant volume for a particular operation. In addition, like many academic books in Japan, the volumes of the history do not contain an index, which can make it time-consuming to search for a particular operation or unit. Despite these shortcomings, the history is still the single most authoritative work concerning Japanese military operations during the Second World War.
Specifically, the following volumes may be the most useful concerning Japanese operations against Australia: Volume 22, Army air operations in the western New Guinea area (Seibu Nyûginia Hômen Rikugun Kôkû Sakusen), which describes the Army air forces’ June 1943 raids on Port Darwin; Volume 26, Navy offensive operations in the Dutch East Indies and Bengal Bay area (Ran'in/Bengaruwan Hômen Kaigun Shinko Sakusen), which describes the carrier and land-based raid on Darwin in February 1942; and Volume 61, Operations of the 3rd Air Army in the Burma/Dutch East Indies area (Biruma/Ran'in Hômen Dai 3 Kôkûgun no Sakusen), which also describes the Army air operations against Port Darwin in 1943. In addition, Volume 7, Army air operations in the eastern New Guinea area (Tôbu Nyûginia Hômen Rikugun Kôkû Sakusen) discusses in detail the decision to commit Army air forces in late-1942 into the south-east Pacific, which theretofore had been a Navy theatre of operations. Finally, Volume 98, History of submarines (Sensuikan Shi) describes the various submarine operations against Australia, including the details of the midget submarine attack on Sydney Harbour.
It is interesting to note that while it is possible to get a relatively detailed picture of the Port Darwin raid of February 1942, the Army’s air raids of June 1943 and the submarine operations from the various volumes of the official history, not much has been written about the Takao/753rd Air Corps and 3rd/202nd Air Corps’ repeated raids on Port Darwin and other targets from bases in the Dutch East Indies. This may be because that operation, while undoubtedly a significant undertaking for the Japanese Navy and certainly a major event for the Australia people affected, was considerably overshadowed in both scale and overall effect on the war by the events in the Coral Sea, at Midway and around Guadalcanal and the Solomons, which took place one after the other during the same time period. Certainly, these three campaigns have been covered in great detail in the official history, while the remarks concerning the Port Darwin operations based in the East Indies were scattered among several volumes. It is also apparently possible that sections describing in detail the attacks against Australia were initially written, only to be cut, along with other sections, during the final editing process, due to budgetary restraints.
Other secondary literature
A number of the participants in the operations against Australia have discussed the operations in their memoirs. For example, KUSAKA Ryûnosuke, the Chief of Staff of the 1st Air Fleet (Dai 1 Kôkûkantai), and GENDA Minoru, Air Staff Officer of the same, took part in the Navy’s February 1942 attack on Port Darwin as officers aboard the Akagi, and have described that event in their respective works.  While the comments in either case are not extensive, they are useful for viewing the operation through the participants’ eyes.
On the other hand, a number of diaries often used by researchers interested in the Pacific theatre barely mention the Australian operations, if at all. UGAKI Matome, Chief of Staff of the Combined Fleet in 1942 and early-1943, mentions in his famous diary only the 19 February air raid and the 31 May midget submarine attack, along with a few comments.  The recently published war diaries of the War Direction Section of the Army General Staff do not mention any of the operations, and the diaries kept by SUGIYAMA Hajime, Army Chief of Staff during the relevant period, also do not mention any of the Australian operations.  This is probably because the Australian operations were a purely military activity, and not of particular concern to higher-level political and military leaders.
Finally, while there is apparently no single-volume general work in Japanese that deals solely with the Australian operations, some do mention it to a certain degree. For example, a history of the Navy’s fighter arm discusses the Port Darwin raids by the 3rd Air Corps from March 1942 onward (as well as the initial 19 February raid by the carrier-based planes) in the context of combat between the Navy’s famed Zero fighter and the British Spitfire.  A large work on the history of Japanese submarines also describes submarine operations, particularly the midget submarine attack in Sydney Harbour, in detail.  Surprisingly, a general history of the Navy’s land-based bombers mentions the operations by such bombers against Australian targets, but does not go into any great detail.  In all of these cases, it was not clearly indicated whether primary sources had been referred to. Generally speaking, it is surprising how little coverage had been given to the Australian operations in books which otherwise covered, for example, the activities of the naval air arm in detail,  considering that for at least two air corps, the Takao/753rd and the 3rd/202nd, it was their only major operation for over a year and resulted in more than just a few casualties.
Any researcher interested in studying the Japanese side of Japan’s operations against the Australian mainland during the Second World War is in a relatively fortunate position as far as source materials are concerned. The virtually-complete availability of the action reports of the naval air units involved makes it possible to study in great detail the aspects of the vast majority of such operations. When these are fleshed out by the official history accounts of the Army air force operations and submarine operations, a near complete picture of such operations from the Japanese side may be grasped. Given the relative lack of secondary literature covering the Japanese aspects of these operations, it may be a promising field of research for scholars studying the Pacific theatre of the Second World War.
1. In fact, the Japanese often referred to the New Guinea – Solomons area as “Northern Australia” (Gôhoku). This can sometimes be misleading; e.g. a file labeled, for example, “Operations in North Australia” often contains documents relating only to operations in the New Guinea – Solomons area.
2. While this essay will not discuss the details of the Japanese operations against Australia, it is necessary to know the approximate dates and, more importantly, the units involved, because most of the primary documents are organized by unit name and date.
3. Unless otherwise noted, therefore, all of the primary sources referred to in this paper are in the possession of the library of the National Institute for Defense Studies.
4. Atene Shobo has recently published an 18-volume set containing reprints (actually, copies) of the battle reports of nearly every unit in the Imperial Japanese Navy, from the Naval General Staff down to individual ships and air corps. Unfortunately, many of the reports of the lower level units had to be abridged, and cover only certain periods; the reports of the Australian operations of the units that took part in them may therefore not all be contained therein.
5. KUSAKA Ryûnosuke, Rengô kantai Sanbôchô no Kaisô (Recollections of the Chief of Staff of the Combined Fleet), Kowado, 1989; GENDA Minoru, Kaigun Kôkûtai Shimatsuki (Naval Air Forces: A Settlement), Bungei-Shunju, 1997.
6. UGAKI Matomei, Sensôroku, Hara Shobo, 1988.
7. Gunjishi Gakkai (Military History Society of Japan), ed., Kimitsu Sensô Nisshi (Secret War Diaries), Kinseisha, 1998; Sanbô Honbu (Army General Staff), ed., Sugiyama Memo, Hara Shobo, 1989.
8. Reisen Tôjôin Kai (Zero Fighter Pilots’ Association), Kaigun Sentoki-tai Shi (History of the Navy’s Fighter Plane Units), Hara Shobo, 1987.
9. Nihon Kaigun Sensuikan Shi Kankôkai (Association for the Publishing of the History of Japanese Navy Submarines), Nihon Kaigun Sensuikan Shi (History of Japanese Navy Submarines), Shinkosha, 1979.
10. IWAYA Fumio, Kaigun Rikujô Kôgekitai (Navy Land-based Attack Forces), Asahi Sonorama, 1996.
11. For example, OKUMIYA Masatake, Kaigun Kôkûtai Zenshi (Overall History of Japanese Naval Air Forces), Asahi Sonorama, 1994.