The spy agency GCHQ is celebrating its centenary on Friday by highlighting little-known wartime eavesdropping and decoding work that took place in five secret locations around the country, from the Kent cliffs to the Derbyshire countryside.

That includes the dangerous work undertaken daily by about 50 linguists, many of whom were women, who listened in to shortwave German naval and airforce radio at Abbots Cliff House near Dover, a site exposed to enemy attack.

Or at Marston Montgomery, a base headed at one point by the agency’s first female commander, Pamela Pigeon, a New Zealander who took over operations in 1943 in a series of wooden huts hidden in the countryside.

Tony Comer, GCHQ’s historian, told the Guardian that about 100 people were based there, “fingerprinting individual German radios, taking advantage of the fact that each crystal at the heart of a radio oscillated slightly differently.

“If you had previously worked out what each radio was used for, it presented an easy way to distinguish between a bomber squadron or simply fighter aircraft approaching without having to decode any messages.”

The 6,000-strong agency – the most secretive of Britain’s intelligence organisations – wants to showcase more of its little-known history beyond the now famous story of the cracking of the German Enigma cipher at Bletchley Park, led by Alan Turing.

It is a history that dates back to the aftermath of the first world war, when politicians – including the prime minister at the time, David Lloyd George – were eager to maintain a capability that had been built up separately by the army and navy.

Facebook Twitter Pinterest A fax intercepted and translated by GCHQ staff during the second world war. Photograph: GCHQ

A year earlier, in 1917, naval codebreakers had cracked the Zimmerman Telegram, an offer from Germany to Mexico to enter the war in return for territories in the US, which, when revealed, helped bring an angry US into the conflict.

Stories about GCHQ’s wartime work are felt to help with the agency’s profile and recruitment following revelations by the whistleblower Edward Snowden of the extent of its surveillance activities.

Six years ago, based on the leaks, the Guardian and other news organisations were able to demonstrate that GCHQ had tapped into fibre-optic cables via a programme named Tempora and helped the US National Security Agency to gain access to the servers of mostly US internet providers in a scheme called Prism.

At the time, the Snowden files revealed the extent of the agency’s ambitions, that it wanted to be able to “exploit any phone, anywhere, any time” and that its “collection posture” included slides listed under the heading “Collect It All”.

Such activities do not feature as part of GCHQ’s historical celebrations – the secret agency’s perception of history closes at the end of the cold war – although some later activities are foreshadowed by what went on between 1939 and 1945.

Facebook Twitter Pinterest Ivy Farm, in Knockholt, Kent Photograph: GCHQ

At Ivy Farm, in Knockholt in Kent, a group of about 80 had the task of listening to “human-made noise” – what Comer described as “any unusual activity on the electromagnetic spectrum” that could amount to a previously unknown form of encrypted communication. Those working there managed to isolate enciphered communications between Adolf Hitler and his field marshals using the Lorenz cipher that was cracked at Bletchley Park.

The site, Comer added, was the first place responsible for the interception of a fax, then an emerging technology used primarily by newspapers to send simple pictures around the world.

“A Japanese press attache in Berlin had sent a description of a typical US bomber formation to a press agency in Tokyo. Staff at Ivy Farm were able to intercept the communication and pass it on to the Americans, so they could adapt,” the historian added.

Other secret locations highlighted by GCHQ include Chesterfield Street in Mayfair, the site of the agency’s first anti-Soviet operations, which began work in 1944, a year before the war ended, and Croft Spa, in the Yorkshire countryside near Scarborough, where signals from enemy ships in the North Sea were pinpointed.