Ultra (cryptography)

Ultra was the secret name used by British military intelligence during World War II for important information they got by breaking enemy codes. This information came from reading encrypted enemy radio and teleprinter messages at a special place called Bletchley Park. The name "Ultra" was chosen because this information was considered even more secret than the highest level of secret in Britain at that time.

The most famous code the Allies broke was the German Enigma machine, but Ultra also included breaking other codes like the Lorenz SZ40/42 and Hagelin machines. To keep the success of their code-breaking hidden from the Germans, British intelligence made up a story about a master spy named Boniface who supposedly provided the information.

Many leaders believed Ultra was very important to winning the war. Winston Churchill credited Ultra with helping the Allies win, and some experts thought it may have shortened the war by several years. However, others think the effect might have been smaller.

Sources of intelligence

Most Ultra intelligence came from reading encrypted radio messages, along with information from radio traffic analysis and direction finding. In the early part of the war, the Germans often used land lines instead of radio, giving Bletchley Park time to learn how to collect and decrypt messages from various radio networks. The main source was German Enigma messages, especially from the Luftwaffe, who used radio more often.

The Germans used different types of Enigma machines for the Army, Navy, Air Force, and other groups, each needing different methods to break. The Polish helped the Allies understand Enigma before World War II began. At Bletchley Park, mathematicians like Alan Turing played key roles in breaking these codes. The Germans also used a different system called Lorenz for important messages between their high command, which the British also managed to break, though this story is less well known than the Enigma story.

Main article: Cryptanalysis of the Enigma

Main article: Cryptanalysis of the Lorenz cipher

Distribution

The intelligence from breaking enemy codes was shared carefully with Allied commanders to keep it secret from the Germans. It started with summaries made at Bletchley Park and sent out under secret codewords like "BONIFACE" for army and air force information, and "HYDRO" for naval intelligence.

In June 1941, the codeword “ULTRA” was chosen to highlight the importance of this intelligence. Special teams called Special Liaison Units (SLUs) were created to deliver this information safely to commanders. These teams took great care to protect the secret, often destroying the information after it was read. By the end of the war, there were about 40 of these units all over the world, connected to Bletchley Park by radio links.

Use of intelligence

Most messages that were decoded contained details that seemed unimportant for military planning. However, organizing and sharing this information was very important. At Bletchley Park, experts kept careful records of everything they found in the messages. They noted things like when and where messages were sent, who sent them, and special codes used.

Ultra intelligence helped the Allies win many important battles. For example, it gave warning about German plans during the Battle of Britain and helped the British Navy win at the Battle of Cape Matapan. It also aided the U.S. Navy at the Battle of Midway and helped plan the Allied invasion of Sicily. Ultra intelligence was valuable because it gave leaders important information about enemy movements and plans before they happened.

Safeguarding of sources

The Allies were very worried that the Axis powers might discover they had broken enemy codes. To keep this secret, they used clever tricks. For example, when planning attacks on supply ships heading to North Africa, they sent out submarines and planes to search for ships. This made the Axis think they were being found by regular scouting, not because the Allies had secret information.

They also used other tricks to hide their knowledge. Sometimes they sent extra search missions to other areas so that their own crews wouldn’t suspect why they always found the enemy ships. Even when they had to act quickly, like attacking a supply convoy from Naples to North Africa, they found ways to make it seem like luck. They even sent fake messages to make the Germans think their codes were still safe. These careful steps helped protect one of the most important secrets of the war.

Role of women in Allied codebreaking

During World War II, many women played a vital role in breaking enemy codes and messages. At Bletchley Park, around 8,000 women made up most of the workers who helped process and translate intercepted messages. In the United States, the Army and Navy also employed thousands of women for similar work in their signal intelligence services.

Unlike the Germans and Japanese, the Allies recognized the important contributions women could make to their war efforts. This included handling large amounts of daily work needed to support the code breakers and keep up with changing enemy communication methods.

Postwar consequences

The discovery of the sunk German submarine U-869 off the coast of New Jersey was helped by analyzing Ultra intercepts. These showed that the submarine had missed messages telling it to change course, so it continued to the eastern coast of the U.S. instead of going to North Africa.

In 1953, a CIA project called Project ARTICHOKE was renamed Project MKUltra. The name "MK" came from the CIA's Technical Services Division, and "Ultra" referenced the Ultra project.

Postwar secrecy

Until the mid-1970s, there was no official mention of Bletchley Park due to the thirty year rule. This meant that the important role of broken codes in many operations was left out of historical records. For example, Winston Churchill’s book The Second World War mentioned Enigma but not that it had been broken.

Ultra intelligence remained secret for almost 30 years after the war. There are a few reasons for this long secrecy. One reason is that after the war, old Enigma machines were sold to some countries, and Britain wanted to keep the machines’ weaknesses hidden. Another reason relates to a mistake made by a past British leader, Stanley Baldwin, who shared secret information in the 1920s, causing other countries to change their codes. Finally, in 1945, Churchill asked people who received Ultra intelligence not to talk about it, to protect future secret operations and to avoid giving the enemy a reason to believe Ultra had caused their defeat.

In 1967, a Polish historian, Władysław Kozaczuk, revealed in his book that Enigma had been broken by Polish experts before World War II. That same year, author David Kahn wrote about cryptography and mentioned that Soviet forces were reading Enigma messages by 1942. He also talked about the capture of a German submarine’s Enigma machine in 1944, giving clues about the large scale of the Allied effort to break Enigma codes.

Public discussion of Bletchley Park’s work became accepted after 1974, when a former staff member, F. W. Winterbotham, published The Ultra Secret. Since then, many books have been written about this secret work, including official histories and personal stories from former codebreakers. Even today, some details remain secret, such as Alan Turing’s last papers on Enigma, which were only released in 2012 due to their ongoing sensitivity.

Historical debates on Ultra

Historians and Holocaust researchers have studied when the Allies learned about the Holocaust and the Nazi extermination camps. After World War II, the U.S. Government passed a law to declassify documents about Nazi war crimes, leading to the release of many secret messages. However, experts found that these messages alone could not have given Allied leaders early warnings about the full scale of the Holocaust.

The existence of Ultra, the secret intelligence from broken German codes, was kept hidden for many years after the war. When the story finally became public, historians began to rethink parts of World War II. For example, one historian said that because British forces could read German messages, they knew the weaknesses of their enemy. Over time, Ultra became widely known, and Bletchley Park, where the code-breaking happened, became a popular place for visitors to learn about history.

There has been much debate about how much Ultra helped end World War II. Some believe that without it, the war might have lasted much longer. Others think the Allies would have won anyway, but perhaps a bit later. Different historians have different opinions, and it is hard to say exactly how many years Ultra may have shortened the war by. Some say it may have helped end the war sooner, while others point out that other factors, like new technology, also played big roles.