Information and Warfare
The histories of information and warfare are closely connected. We do not know of a time when warring peoples have not sought to gain the upper hand over their opponents by gathering intelligence and passing messages. Technologies have changed drastically, but there is a common thread between the legend of Pheidippides during the Battle of Marathon in 490 BC and the use of drones and encrypted digital messages today.
Although the mobilisation of information in warfare is as old as civilisation, there have been obvious moments of change. The Second World War was one of these, as it saw a remarkable expansion of data collection and analysis by states around the world. It was a conflict where information was viewed as a weapon of war.[1]
In practice, there were three weapons: propaganda, intelligence, and censorship. Propaganda was the most obvious and has been the best studied by historians. Intelligence was the most hidden, but has attracted historians interested in espionage and codebreaking. Censorship, by contrast, worked in plain sight and remains surprisingly underexplored by historians.
Censorship and Security
The idea of using censorship to control information was established well before the Second World War. In fact, a secret history of postal censorship in the First World War noted that Oliver Cromwell had designed a General Postal Service in part because it would allow inspectors to “discover and prevent many dangerous and wicked designs which have been and are daily contrived against the peace and welfare of the Commonwealth”.[2]
Modern censorship practices are more recent. At the turn of the twentieth century, newspaper reports from the Boer War had been censored in the field and journalists were vetted before being permitted to travel to South Africa.[3] This experience led to the creation of the Defence—or “D”—Notice system, which allowed military authorities to proscribe certain subjects in the interests of national security.[4]
The First World War saw the extension of British censorship to cover private communications. This was initially limited to mail destined for enemy countries. But the system was gradually expanded to include almost all mail entering or leaving the British Isles and occasionally letters sent from one part of the United Kingdom to another. The power to intercept mail in this way had been confirmed by the Post Office Act of 1908, which required the Postmaster General to detain mail if required to do so by warrant. The Telegraph Act 1885 contained a comparable rule for all forms of telegraph communication.[5]
Media censorship was, despite practical difficulties, a relatively simple task. Newspapers, periodicals, and books were designed to be made public and censorship could be justified by the need to remove information of military value. The censorship of private communication raised trickier questions. Although it might be justified on the same principle, it intruded into the personal lives of millions of mostly innocent people.[6]
Censorship Policy
In the run up to the Second World War, military authorities looked back to 1914–1919 for lessons about how best to monitor such communication. But the Postal and Telegraphic Censorship (P&TC) department set up in the Second World War operated on an even greater scale.
The system operated in accordance with the government’s Regulations for Censorship (1938).[7] This document—known as “The Pink Book”, or more informally as “The Bible”—provided the basis for the instructions given to P&TC staff.[8] The regulations clearly established the security objectives of the censorship system, but provided a degree of flexibility in interpretation. This freedom allowed the director of P&TC, the former solicitor Edwin Herbert, to exercise censorship with a degree of pragmatism.
The main objective was to ensure security by stopping communication that contained material of potential benefit to the enemy, whether this was purposeful or not. The subjects that came under this heading were wide-ranging. Censors were told to stop any communication that provided information about military operations, troop movements, shipping, the production of armaments, or the location of industrial sites. But they also had the power to stop anything that “might prejudice British policy, prestige or relations with other powers, or which might adversely affect British or Allied morale”.[9]
As in the First World War, censorship applied to both terminal and transit mails—the first category refers to post from the UK to be delivered abroad, or from abroad to be delivered in the UK; the second refers to post that passed through the UK on its way from one country to another. However, there were more frequent “snap checks” of internal mail and an amended version of the Regulations for Censorship allowed increased domestic censorship from 1942 onwards.[10]
As its name suggests, P&TC also had to adapt to advances in telegraph and telephone technologies which had created new potential battlefields in the war of information.
P&TC operated throughout the Second World War, although responsibility passed between various hands. It worked under the Director of Military Intelligence from September 1939 until April 1940, and subsequently under the Ministry of Information until April 1943. It then operated as a separate department until its closure at the end of September 1945.
The Censorship Process
It is worth considering the actual process of postal censorship, as it provides a window into the extent to which information could be controlled during the war.
Censorship began when a sample of letters was extracted from the mail. These were delivered to “Examiners” in bundles of twelve. Each letter was examined in turn. The Examiner checked the address, used a paper knife to open the envelope, checked for any hidden writing, read the letter, and decided what to do next. If the letter contained nothing of interest, it was classified as harmless correspondence and sent on its way. But if it contained information with either security or intelligence value, it was passed to a “Duty Assistant Censor”. It was their job to decide if a letter contravened the Regulations for Censorship and whether it could be made safe by removing the offending passage. In more troubling cases, the censor had the right to “condemn” the letter, or to pass it to the security services.[11]
The handbooks and guides that form part of Censorship: Policy and Practice During the Second World War are a reminder that censorship was never an automatic process. It was instead dependent upon the judgement and discretion of the thousands of individuals who spent the war reading other people’s writing.
Open Censorship
Because the censorship of private letters raised questions about personal liberty, those responsible for the system believed that people should be told when items had been censored. All letters that passed through the system were thus stamped, while letters that were deemed undeliverable were returned to the sender with a slip explaining the decision. Censors were asked to condemn letters only in serious circumstances.[12]
A similar procedure was applied to telegrams. Most were simply read and passed, while those which were deemed a minor risk had the wording altered. This practice could cause problems. In late 1944, a telegram from London to Basel was flagged for containing a suspected coded message about a German town behind Allied lines. It turned out that the message had been altered by a censor, who had accidentally turned the vowels into a mathematical pattern.[13]
Intelligence Gathering
The P&TC did not just look for codes. As the previous example suggests, censored letters could also be put to more clandestine uses and censors were asked to flag any letters that contained useful intelligence.
The information gleaned was used in two different ways. The first involved working with the security services to collate information on individuals and organisations regarded as suspect. From 1940, the Information and Records Branch of the P&TC included staff specifically working on “Watch Lists”. It acted as a nexus between censorship and the security services, providing censors with the names of individuals whose communication should be closely monitored. This list contained 1,681 names in April 1941, sorted using card indexes.[14]
The second way intelligence was used was to assess public opinion about the war. Starting in December 1939, P&TC compiled regular reports on public attitudes based on information from private letters. These reports formed an important part of the Ministry of Information’s Home Intelligence activities and were regularly cited in the weekly reports that Home Intelligence produced from 1940 onwards.[15]
A Global Network
While its activities centred on the United Kingdom, the Second World War was a global conflict and the P&TC was part of a network that spread through the British empire, into Allied countries, and eventually into occupied territory.[16]
By the end of the war, there were six distinct areas of activity: censorship throughout the British empire; “Joint Allied Censorships” (Anglo-Egyptian, Anglo-Iraqi, Anglo-Soviet-Persian); “Censorship in Allied countries”; “Allied Censorships in Occupied Enemy Territories”; “Censorship in Neutral Countries”; and Censorship in “Enemy, Enemy Occupied and Satellite Countries”. In each case, local censorship offices were set up, with some British censors sent overseas to manage local staff.[17]
The practices of censorship adopted in each area inevitably differed, but Edwin Herbert believed that the system provided the allies with “world-wide control of communication”.[18]
Historical Importance
Postal and Telegraph censorship was a relatively hidden part of the Second World War, but it operated on a global scale and revealed things that were deemed to be of life and death importance.
The documents in Censorship: Policy and Practice illustrate the link between censorship and security. This collection likewise provides various avenues to explore, from the development of censorship policy to its use in intelligence gathering. Taken together, these analytical enterprises offer an opportunity to restore Postal & Telegraph Censorship to its former status as a key weapon of war.
[1] Simon Eliot and Marc Wiggam, ed., Allied Communication to the Public During the Second World War: National and Transnational Networks (London: Bloomsbury, 2020), 1. This will be expanded in Simon Eliot and Henry Irving, ed., Information at War (forthcoming).
[2] London, The National Archives (TNA), DEFE 1/131, “Report on Postal Censorship during the Great War, 1914—1919,” 7.
[3] Jacqueline Beaumont, “The British Press and Censorship during the South African War 1899—1902,” South African Historical Journal 41, no. 1 (1999): 267–89.
[4] Nicholas Wilkinson, Secrecy and the Media: The Official History of the United Kingdom’s D-Notice System (London: Routledge, 2009).
[5] TNA, DEFE 1/131, “Report on Postal Censorship during the Great War, 1914–1919,” 2 and 79.
[6] Graham Mark, British Censorship of Civil Mails during World War I, 1914–1919 (Bristol: Stuart Rossiter Trust Fund, 2000).
[7] TNA, DEFE 1/132, Regulations for Censorship, 1938.
[8] TNA, DEFE 1/136/11, Handbook of Instructions and Orders for the Postal Censorship Staff, undated.
[9] TNA, DEFE 1/136/11, Handbook of Instructions and Orders for the Postal Censorship Staff, 4.
[10] TNA, DEFE 1/53, H. D. P. Francis, “Revision of Regulations for Censorship 1938,” 20 December 1945.
[11] TNA, DEFE 1/136/11, Handbook of Instructions and Orders for the Postal Censorship Staff, 9–14.
[12] A label on the outer envelope read: “Returned to sender by the censor for reason explained in memorandum enclosed in the cover”.
[13] TNA, DEFE 1/416, A. F., Text of Telegram, 8 December 1944.
[14] TNA, DEFE 1/406, History of the Information and Records Branch: Postal & Telegraph Censorship Department, June 1940–December 1944.
[15] Eliot and Irving, ed., Information at War (forthcoming).
[16] See, for example, TNA, DEFE 1/82, Definition of United States and British Responsibility for Censorship of Civilian Communications in Eur-African Areas [October 1943].
[17] Instructions for overseas staff are included in DEFE 1/42, “Record of Instructions to Censorship Staff (Overseas)”.
[18] Eliot and Irving, ed., Information at War (forthcoming).