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 very secret.

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 helped end the war sooner. However, others think the effect might have been smaller.

Sources of intelligence

Most Ultra intelligence came from reading encrypted radio messages. They also used traffic analysis and direction finding. In the early part of the war, the Germans often used land lines instead of radio. This gave Bletchley Park time to learn how to collect and decrypt messages from 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 needed 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. The British also managed to break this, 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. It started with summaries made at Bletchley Park and sent out under secret codewords.

In June 1941, the codeword “ULTRA” was chosen to show how important this intelligence was. Special teams called Special Liaison Units (SLUs) were created to deliver this information safely to commanders. These teams worked hard to keep 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.

Use of intelligence

Most messages that were decoded had information that did not seem very important for planning battles. But it was still very important to organize and share what they learned. At Bletchley Park, experts kept good records of everything they found. They wrote down things like when and where messages were sent, who sent them, and what special codes they used.

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

Safeguarding of sources

The Allies were worried that the Axis powers might find out they had broken enemy codes. To keep this a secret, they used clever tricks. When planning attacks on ships going 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 helped break enemy codes and messages. At Bletchley Park, about 8,000 women were most of the workers who processed and translated messages. In the United States, the Army and Navy also used thousands of women for this important work.

The Allies knew women could help a lot during the war. Women did much of the daily work to support code breakers and keep up with enemy communication changes.

Postwar consequences

The discovery of the sunk German submarine U-869 off the coast of New Jersey was helped by looking at 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, no one talked about Bletchley Park because of the thirty year rule. This meant that the important job of breaking codes was left out of history books. For example, Winston Churchill’s book The Second World War talked about Enigma but not that it had been broken.

Ultra intelligence stayed secret for almost 30 years after the war. There are a few reasons for this. One reason is that after the war, old Enigma machines were sold to some countries, and Britain did not want them to know the machines had weaknesses. Another reason is that a past British leader, Stanley Baldwin, shared secret information in the 1920s by mistake. This made other countries change their codes. Finally, in 1945, Churchill asked people who got Ultra intelligence not to talk about it. He wanted to keep future secret operations safe and to make sure the enemy did not think Ultra had helped defeat them.

In 1967, a Polish historian, Władysław Kozaczuk, wrote a book saying that Enigma had been broken by Polish experts before World War II. That same year, author David Kahn wrote about secret messages and said that Soviet forces were reading Enigma messages by 1942. He also talked about capturing a German submarine’s Enigma machine in 1944.

Public discussion about Bletchley Park’s work became normal 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. Even today, some details are still kept secret, like Alan Turing’s last papers on Enigma. These papers were only released in 2012 because they were still sensitive.

Historical debates on Ultra

Historians have looked at when the Allies learned about the Holocaust and the Nazi camps. After World War II, the U.S. Government shared many secret messages. But these messages did not tell Allied leaders everything about the Holocaust early on.

Ultra was the name for secret information from broken German codes. It stayed secret for many years after the war. When people finally learned about it, historians started to think differently about some parts of World War II. For example, British forces could read German messages, so they knew some of their enemy's plans. Over time, Ultra became well-known, and Bletchley Park, where the code-breaking happened, became a popular place to visit and learn history.

There has been much talk about how much Ultra helped end World War II. Some think the war might have lasted longer without it. Others believe the Allies would have won anyway, maybe just a little later. Historians have different ideas, and it is hard to know exactly how much Ultra helped shorten the war. Some say it helped end the war sooner, while others say other things, like new technology, also mattered a lot.