What types of communications were used in World War 2?

Answer 1

Radio was the most important. Every combatant nation encrypted its messages in as complex a code as possible, knowing the enemy would be listening for broadcasts and trying to crack the code to read the messages. For many years after the war it was kept a secret how successful the Allies had been at decrypting enemy transmissions. The Germans used the Enigma machine to encrypt their messages, which they believed to be unbreakable without the message "key" (the initial setting of the complex machine) which was changed daily. But the British, with help from Poles (whose postal service had used commercially purchased early versions of the Engima), using one of the world's first computers, were eventually able to read a large portion of this traffic. American codebreakers were able to decrypt large amounts of Japanese traffic as well, which contributed greatly to the decisive victory at Midway, and made the killing of Admiral Yamamoto possible. In many armies forward observers (FOs) with the frontline troops were able to use their radios to call up the artillery and correct its aim to bring artillery fire directly on to the enemy. This had not been possible in previous wars. The standard radio of US ground troops was the SCR-500 (Signal Corps Radio Model Number 500) which was a very heavy unit, about seventy pounds, and not always reliable. The "walkie-talkie" first made its appearance in WWII with US troops. These were huge contraptions, about the size of a loaf of bread. There were no printed circuit boards, no transistors yet, so all radios of every type had a bunch of vacuum tubes inside them, and were very heavy and took time to warm up before use. The US also had "field telephones", as they had in the First World War, which had to be connected to one another by wire. This offered the advantage that the enemy could not hear what was said, unless he infiltrated and cut the wire to install his own headset, something the Japanese often did and the Germans sometimes. The wire could be cut, by shellfire explosions or infiltrating enemy soldiers, and when the phone went dead somebody had to go out and run their hand along the wire until they found and spliced the break. By late in the war the US had perfected using FM radios to allow ground controllers with tank units to speak directly with pilots in aircraft flying ground attack support, and thus direct their attack onto the enemy. The US made around 70 large scale amphibious attacks during the war, and forward observers landing on the beaches with the assault troops were able to call in naval gunfire from the ships off the invasion beaches. All American and British tanks had radios in them. In the Russian Red Army only the unit leaders tanks were radio equipped. Airplanes of course had radios, but Americans on bombing missions tried not to use them much, because every nation had the ability to use RDF - radio direction finding - to locate and pinpoint the source of a radio transmission, which would draw enemy fighter planes to attack the bomber formation. Similarly, spies operating in occupied Europe spying on the Germans had radios, but they tried to use them only at the times specified for their transmissions, and to send their messages very quickly, to give as little chance as possible for Gestapo agents in RDF vans riding around the cities to pinpoint their location. Ships at sea often observed radio silence, to avoid giving away their position, as the Japanese did on the way from Japan to attack Pearl Harbor. Ships at sea could use semaphore flags to speak to each other. This was a specially trained signalman with a flag in each hand, which he held in positions to spell out each letter of a message. At night, powerful spotlights with a shutter device over the front could be used to "blink" morse code messages between ships. The US Navy and other navies also had TBS - "talk between ships" - a low powered system that was supposed to allow radio communication between ships in a formation, which was not supposed to carry too far, and thus ought not to be picked up by enemy listening stations and give away the ships' position. But atmospheric effects, such as "skip", could in fact carry those TBS transmissions a very long way on some occasions. Within the US regular telephone lines could be used, and anywhere telephone lines reached teletypewriters could be used to send messages. Telegrams were still important. Most next of kin of US servicemen killed or wounded were notified by a telegram from the War or Navy Departments. Wives on the home front lived in dread of seeing the telegram delivery guy appear on their doorstep. Between the US and Europe, ND the US and Hawaii, there were undersea cables, the transatlantic ones dating from the late 1800s, which could be used to send "cable" messages which the enemy could not intercept.