Title: World War I cryptography
Content:  Codes and ciphers were used extensively in World War I. The decoding by British Naval intelligence of the Zimmermann telegram helped bring the United States into the war. Trench codes were used by field armies of most of the combatants (Americans, British, French, German) in World War I. The most commonly used codes were simple substitution codes. More important messages generally used mathematical encryption for extra security, though. The use of these codes required the distribution of codebooks to military personnel, which proved to be a security liability since these books could be stolen by enemy forces.
Title: Code talker
Content:  of encryption and decryption of communications in front line operations during World War II. There were two code types used during World War II. Type one codes were formally developed based on the languages of the Comanche, Hopi, Meskwaki, and Navajo peoples. They used words from their languages for each letter of the English alphabet. Messages could be encoded and decoded by using a simple substitution cipher where the ciphertext was the native language word. Type two code was informal and directly translated from English into the native language. If there was no word in the native language to describe a military word, code talkers 
Title: Telegraph code
Content:  so that messages could be sent between them without the need for operators to recode them at borders. The Gerke code was adopted for this purpose. In 1865, a conference in Paris adopted the Gerke code as the international standard, calling it International Morse Code. With some very minor changes, this is the Morse code used today. The Cooke and Wheatstone telegraph needle instruments were capable of using Morse code since dots and dashes could be sent as left and right movements of the needle. By this time, the needle instruments were being made with end stops that made two distinctly 
Title: American Morse code
Content:   American Morse Code — also known as Railroad Morse—is the latter-day name for the original version of the Morse Code developed in the mid-1840s, by Samuel Morse and Alfred Vail for their electric telegraph. The "American" qualifier was added because, after most of the rest of the world adopted "International Morse Code," the companies that continued to use the original Morse Code were mainly located in the United States. American Morse is now nearly extinct—it is most frequently seen in American railroad museums and American Civil War reenactments—and "Morse Code" today virtually always means the International Morse which supplanted American Morse.
Title: World War II cryptography
Content:  Cryptography was used extensively during World War II because of the importance of radio communication and the ease of radio interception. The nations involved fielded a plethora of code and cipher systems, many of the latter using rotor machines. As a result, the theoretical and practical aspects of cryptanalysis, or codebreaking, were much advanced. Possibly the most important codebreaking event of the war was the successful decryption by the Allies of the German "Enigma" Cipher. The first break into Enigma was accomplished by Polish Cipher Bureau around 1932; the techniques and insights used were passed to the French and British Allies just before the outbreak of the war in 1939. They were substantially 
Title: Code talker
Content:  The first known use of code talkers in the US military was during World War I. Cherokee soldiers of the US 30th Infantry Division fluent in the Cherokee language were assigned to transmit messages while under fire during the Second Battle of the Somme. According to the Division Signal Officer, this took place in September 1918 when their unit was under British command.
Title: Welsh language
Content:  Secure communications are often difficult to achieve in wartime. Just as Navajo code talkers were used by the United States military during World War II, the a Welsh regiment serving in Bosnia, used Welsh for emergency communications that needed to be secure.
Title: Trench code
Content:  Trench codes (a form of cryptography) were codes used for secrecy by field armies in World War I. Messages by field telephone, radio and carrier pigeons could be intercepted, hence the need for tactical World War I cryptography. Originally, the most commonly used codes were simple substitution codes, but due to the relative vulnerability of the classical cipher, trench codes came into existence. (Important messages generally used alternative encryption techniques for greater security.) The use of these codes required the distribution of codebooks to military personnel, which proved to be a security liability since these books could be stolen by enemy forces. 
Title: American Morse code
Content:  "German and American" code; some lines with the state system seem to have generally used one, some the other (and a few lines had Wheatstone equipment and so did not use Morse Code at all). In the late 1890s, radio communication—initially known as "wireless telegraphy"—was invented, and used Morse Code transmissions. Most radio operators used the version of the Code that they were most familiar with—the American Morse Code in the United States, and Continental Morse in Europe. However, because of the long range of radio signals, a single international standard was needed, especially for seagoing vessels. At the Radiotelegraphic Convention meeting in London in 1912, the section of the Convention covering 
Title: American Morse code
Content:  than the Gerke code. The Gerke code was adopted as a standard for transmission over cables by the Austro-German Telegraph Union (which included many central European states) at a conference in 1851. It was necessary to have a common code as the Union had also agreed to direct connection of cables across borders (as opposed to recoding and retransmission by an operator). The code was adopted as the European standard in 1865, and was known at first as "Continental Morse," although as its use spread it also became known as "International Morse." At this point the original Morse Code started to be called American Morse, to differentiate between the two main standards. 

Question: who used morse code in world war 2?
Answer: naval bases.
warships.