The A to Z Challenge asks bloggers to post 26 posts, one for each letter of the English alphabet, in April. Most of us choose to make these posts on a particular theme. My theme for 2023 is 1943 Washington D.C., the setting of the novel that I’m writing. Visit daily in April for a new post on my topic.

S is for Signal

The characters in my novel are codebreakers at Arlington Hall, working for an agency in the Army Signal Corps.

First, let’s figure out what we mean by “signal.” It’s all about communication and follows the path of communication technology in the 19th and 20th centuries.

The Army Signal Corps has existed since 1860. At that time, the Corps was responsible for developing a system of visual communication on the battlefield. They signaled messages in symbols that used flags in the daytime and torches at night. When the telegraph became a viable communication tool in the midst of the Civil War, the Army Signal Corps took responsibility for that system, too.

Soldiers employing signal flags. From the Library of Congress.

The first national weather service was operated by the Army Signal Corps, since weather reports were important information items that needed to be communicated. Eventually, the Weather Bureau for civilians was shifted to the Department of Agriculture (Now the National Weather Service is part of the National Oceanic and Atmospheric Administration under the Department of Commerce) while the Army Signal Corps continued to be responsible for military weather reports.

During the Spanish-American War, the telephone was the newest communication technology to be employed by the Army Signal Corps.

It was the Army Signal Corps who received the first funding and responsibility to figure out whether new-fangled aeroplanes had a role to play in the military. They contracted with the Wright Brothers to develop the first military aircraft and also developed the Military Aviation pilot certification program, before passing the program off to the new Army Air Service during World War I.

World War I recruiting poster for the Army Signal Corps. From the Library of Congress.

The “Hello Girls” were bilingual (English and French) switchboard operators stationed in France for the Army Signal Corps during World War I.

Hello Girls operating switchboards in Chaumont, France during WWI. From Wikipedia.

Between the Wars, the Army Signal Corps developed both radar and radio for information and communication purposes.

Radar equipment was commonly called “radio” in order to obscure its true purpose of gathering information on the movement of enemy aircraft. The Army Signal Corps trained radar operators.

The Army Signal Corps also developed the first FM backpack radio and trained operators to use them.

World War II recruiting poster for the Army Signal Corps. From the National Archives.

Besides communicating with one’s own troops, the military is interested in monitoring the communications of the enemy. Part of communication, then, is to keep one’s own messages private while finding ways to eavesdrop on the enemy. These efforts require code making and code breaking.

The US was hampered in its codebreaking abilities between the Wars by this famous statement from Secretary of State Henry L. Stimson: “Gentlemen do not read each other’s mail.” He shut down the U.S. Cipher Bureau, a joint operation of the State Department and the Army in 1929.

The Army Signal Corps developed a new unit in 1930 to work on codes and cipher mechanisms for the Army to use in its own communications. This was the Signal Intelligence Service.

SIS was a tiny unit until war broke out in Europe in 1939. By then, the unit had begun working on decryption techniques for the new machine-enciphered communication systems.

When the US entered the war, it became apparent that SIS was going to need a lot more employees to handle the decryption and translation of intercepted communication signals received by radio operators in the Army Signal Corps. In June 1942, SIS took over Arlington Hall.

Arlington Hall was originally a junior college for women. From the Library of Congress.

To get back to the topic of 1943 — that’s the year that the employees of the Signal Intelligence Service (SIS) had to adjust to a succession of new names.

Here are the names that were in use during 1943 as listed by this Guide to Federal Records at the National Archives.

• September 1942 – March 1943: Signal Security Branch (SSB)
• March 1943 – June 1943: Signal Security Service (SSS)
• July 1943 – the end of the war: Signal Security Agency (SSA)

You can imagine that this period makes it hard to write about the history of the agency that continued to function in Arlington Hall. The books I’ve read tend to settle on either SIS from the beginning of the war or SSA from the end. Or, they do what I normally do and use “Arlington Hall” as a stand-in for the work that was done in that place, regardless of the bureaucratic structure.

After World War II, the name changed again to the Army Security Agency before it and other related activities in the military and the rest of government was united under the National Security Agency in the 1950s.

The Army Signal Corps exists to this day, managing all the modern communication technology required by the Army and any joint and coalition operations involving the Army.