Group 3: History
To what extent did breaking code JN-25 and code ULTRA give aid to the Allies in the Pacific and Atlantic theatres of World War Two?
Word Count: 3746
This extended essay has the subject of Code Breaking Intelligence. When studying the Second World War, the phrase ‘code breaking’ is not highlighted as a significant factor, so this investigation is to assess the contribution of code intelligence in the Second World War. The main question being: To what extent did breaking code JN-25 and code ULTRA give aid to the Allies in the Pacific and Atlantic theatres of World War Two?
The scope of this investigation is confined to two specific ...view middle of the document...
Word Count: 282
Battle of the Coral Sea 7
Battle of Midway 9
Death of General Yamamoto 12
Many factors contributed to the Allied victory over the Axis powers of the Second World War. A significant factor that is rarely brought to attention in the study of the war is the role that code breaking intelligence played. Therefore, my investigation will attempt to discover to what extent breaking codes JN-25 and ULTRA aided the Allies in the Second World War? What is known is that the intelligence from these codes was used during the war, but was it valuable to the Allies and did they have an effect on the outcome of the war? The first code was the Japanese JN-25 broken by the Americans and used during the Battle of Coral Sea and the Battle of Midway in the Pacific Theatre. The JN-25 intelligence also contributed to the death of General Yamamoto over the Solomon Islands. The second code was the German ULTRA deciphered by the British and used in their fight against the threat of U-boats in the Atlantic Theatre. In this paper I will discuss the codes that were predominately broken, the situations in which this intelligence was adopted and analyse if the breaking of these codes had an effect on the outcome of the war and if it was beneficial for the Allies.
Japanese expansion was an ever growing threat to the Americans, and ultimately the Allies. The Japanese, situated on their island off Korea, were constantly in need of resources due to the supplies being exhausted within their own borders. The very enticing situation of the Philippines, which was very rich in oil sources, was Japan’s next target, the only thing that was hindering the efforts of the Japanese was the ‘sleeping giant,’ more commonly known as the United States. The U.S. Navy was extremely powerful and if the Japanese intended to acquire the Philippines they needed to eliminate America’s seaborne threat. The plan to attack Pearl Harbour derived from this need, as the commander of the Japanese Fleet General Isoroku Yamamoto planned and initiated the surprise attack on Pearl Harbour with the goal of targeting American carriers. The Japanese victory was limited, as most of the Pacific Fleet was destroyed, but they failed to sink American carriers, as they were not present at the time of the attack. Not only did this decrease the naval threat, it also significantly lowered the moral of the Americans.
This was changed by the breaking of the Japanese code JN-25, which came to be known as the turning point of the war in the Pacific. In 1939 the Americans came across a new Japanese code that Washington code breakers could not decode; they dubbed it JN-25. JN-25 was the 25th Japanese Navy code that the Allies had encountered. This cipher was purely for the use of...