Signals Intelligence in the 21^st Century is now one of the most complicated ways of collecting and countering the collection of data. Although, the Battle of Coral Sea is an example for how at the time RADINT the predecessor of SIGINT can drastically impact the battlefield. Without the decryption of the JN25, Red and Purple codes used by the Japanese who knows what could have happened to Port Moresby and the southern Pacific during the war. Yet, the decryption was made possible by the U.S. Signals Intelligence Service (SIS), British decryption out of Bletchley Park, the Australian Signal Corps and New Zealand Signal Corps. Between the four nations the Special Intelligence Bureau was created to share the intercepted Japanese messages that each country was collecting.[viii] The difference with the Japanese codes compared to the German codes was that Enigma the German cipher machine was used to encrypt codes. The Japanese instead for their JN-25 code it included an encrypted codebook for diplomatic messages.[ix] The codes were then additionally re-encrypted a second time with another code book with the second set of codes using ‘false’ numbers so that the receiving member would have to use a correlating additive table to reveal the underlying codes message.[x] Cryptologists and mathematicians from each country joined with military organizations to break the JN25 code after the Red and Purple codes had already been broken. This amount of assistance was necessary since with the double encryption, without the additive aid, the code breakers would have to break the first cipher then the messages themselves.[xi] Although at first initial efforts to break the code were unsuccessful decrypting operational messages the U.S. and the British were able to keep track of Japanese navy allowing them to monitor the order of battle in the theater.[xii] Later in the effort to break the JN25 code other messages were able to be decrypted indicating the Japanese intent to spread its empire to the south-east of the Pacific, this allowing the allies to build up additional forces to combat the Japanese expansion.[xiii] As there was an increase in radio traffic, the Australian and U.S. Navy SIS was able to identify “numerous indications which point to an impending offensive from Rabaul base”.[xiv] This intelligence was enough for the U.S. to then place additional assets in the south Pacific which we know now as what turned up to be the battle at Coral Sea.  The combined effort between the four nations is the lesson in itself that not only SIGINT but shared intelligence between the nations is critical in order to affect the war effort; “It was in the Battle of the Coral Sea that signals intelligence came of age, demonstrating its capacity to predict the enemy’s intentions will in advance and with remarkable accuracy”.[xv]

Applications for the 21^st Century Pacific Theater

To apply the Battle of Coral Sea to the Indo-Pacific region in the 21^st century one of the most critical lessons is that the United States and their allies must maintain multi-dimensional intelligence collection capabilities. In World War II collection capabilities relied on RADINT and reconnaissance aircraft flights but now the United States and the other allied countries have significant upgrades in technology, but the lesson stands true. For the 21^st century upgrading and maintaining a robust SIGINT network that can be shared between the allied countries will allow for indications and warnings of potential Chinese or other actors intentions. To compliment this a stress on space-based collection capabilities namely satellites is a field that has been forgotten but is one of the most significant players in the theater. Having a dominant presence in space is what will ensure that the United States has intelligence collection capabilities in their “back pocket” that many other countries in the world do not have. Lastly, placing sufficient airborne ISR aircraft in the theater will allow for an overlap and extension of collection capabilities. Aircraft such as the MQ-9, U-2, RQ-4, RC-135 and many more robust collection capabilities need to be massed around the high interest area in order to best support war planning and provide additional intelligence collection to inform military leaders and policy makers.

Signals Intelligence also impact today in that the United States has a vast amount of military power but, without SIGINT and information sharing data between New Zealand, Australia, Japan, South Korea, the United Kingdom, and the Philippines serious consequences may ensue. It is crucial to share information since all of these nations have a part to play in a conflict against the primary aggressor in the area of operation, China. Like before the Battle of Coral Sea the nations working together to break the Japanese codes, having overlapping, and robust SIGINT collection networks in the theater and sharing the information may provide Chinese intent, military actions and potential expansion or planning in the area.  

Not only does the United States and its allies need ISR but ensuring a presence of overlapping and sophisticated defensive systems will ensure the survival of the forces already in the theater. One of the more significant tactics during the Battle of Coral Sea that the United States used was having the aircraft carriers close enough to the other destroyers and support ships that all anti-aircraft guns could support the effort. This same principle is needed in a new age conflict of having counter ballistic missile systems, anti-aircraft systems, anti-submarine, and counter-surface warfare capabilities. Employing these types of overlapping defenses will increase the number of remaining forces if a surprise attack or devastating blow from advanced technology occurs at the start of a major conflict. Furthering this effort, the burden does not only need to rely on the U.S. military but using multi-nation partnerships and defenses will also assist in large conflict in the Indo-Pacific.

Conclusion

Overall, the Battle of Coral Sea as the first aircraft carrier battle in history holds many stories to be told, and each one of them providing an essential lesson that fundamentally can impact warfare today. Studying the tactics conducted by the United States and the Japanese during the battle and applying them today can assist in the war planning and shaping the mentality that is required for large scale conflict in the largest geographic theater on the planet. Such lessons like using and maintaining a robust SIGINT network, defensive network and a combined multi-national partnership may not prevent a war, but if a conflict were to arise the allied powers would be significantly more prepared by learning from previous engagements in the theater.

Author Biography: 1^st Lt Brendan H.J. Donnelly, USAF

Lieutenant Donnelly is an intelligence officer stationed at Cannon AFB, NM. He has held intelligence supervisor roles at Cannon AFB and Special Operations Forces Africa. He graduated Bowling Green State University, with a Bachelor of Arts of Sciences, majoring in History.

References