Newly surfaced documents describe a Swiss military assessment circulated in late 1946 that alleged British and American plans to strike Soviet forces in Central and Eastern Europe with conventional and nuclear weapons. The material, identified by the Daily Mail among records at the National Archives in Kew, was read aloud during a meeting in Prime Minister Clement Attlee's Commons office on Nov. 5, 1946, according to notes of the session. Attlee is recorded as dismissing the Swiss paper as "entirely fictitious."
The annex, marked "top secret" in the Swiss file and referenced in the meeting notes, outlines a two‑phase counter‑action. In the first phase it calls for destruction of bridges, railway stations and nodal points across territory described as between the Elbe, Danube and Vistula rivers. The second phase would concentrate air operations on Poland while continuing tactical strikes in the first zone. The Swiss paper said the Anglo‑American plan would rely in part on 400 de Havilland Mosquito fighter‑bombers carrying atomic weapons, supported by thousands of heavy and medium bombers and fighters, and estimated the action could "paralyse the points of departure" of a Soviet offensive for 30 to 45 days.
The archival notes record that Winston Churchill, attending as a former prime minister, read the document to Attlee and senior officials and emphasized the need to limit knowledge of its contents. Present at the meeting were Foreign Secretary Anthony Eden, General Hastings Ismay and other wartime colleagues. The notes say Churchill had obtained the paper from a Swiss staff officer with the consent of Swiss military authorities.
The Swiss assessment framed the alleged plan as a pre‑emptive or counter measure to massive Soviet forces stationed across Germany, Austria, Hungary, Poland and the Baltic states. It estimated Soviet strength at 130 divisions and 50 armoured brigades and concluded that a conquest of Western Europe by the Soviet Union was a practical possibility unless decisive countermeasures were taken.
The document recorded U.S. participation as essential and said American air forces would not be ready to engage in the operation until about June 1947. It estimated a requirement of "up to 200 atomic bombs" in the first phase and additional nuclear strikes in the days that followed.
Contemporary archival and historical records, however, cast doubt on key details in the Swiss paper. The United States possessed only a handful of nuclear weapons in 1946; public records indicate the U.S. stockpile numbered in single digits that year and the Soviet Union did not test its first atomic device until 1949. Britain had not yet developed its own atomic bomb. Attlee told the meeting that no such plans had been worked out and that it was impossible to assemble such forces in Europe because Allied manpower and equipment were engaged elsewhere, according to the notes.
Historians have long documented earlier British contingency planning against the Soviet Union, most notably Prime Minister Churchill's 1945 directive that produced "Operation Unthinkable," which envisaged a surprise Allied attack to push Soviet forces east of the Oder and Neisse rivers. Unthinkable, prepared in July 1945, envisaged massed armoured formations and even proposals to rearm German units; it was rejected by British military chiefs and the United States, which would not support an effort to drive Soviet troops from Eastern Europe by force.
The 1946 Swiss annex differs in scope and timetable from the Operation Unthinkable papers released by the National Archives in 1998. The newly reported file focuses on an alleged combined Anglo‑American air campaign that would rely heavily on strategic bombing and nuclear strikes to buy time for Allied forces to mobilize.
The meeting notes also record Churchill's postwar concerns about Soviet intentions and his effort to alert political leaders to the changing balance of power after the defeat of Nazi Germany. Churchill had warned months earlier that an "iron curtain" had descended across Europe, language that became emblematic of the emerging Cold War. The archival notes include Churchill's earlier telegrams and letters expressing anxiety about the shift of U.S. forces to the Pacific and the strategic implications for Europe.
Participants in the 1946 Commons meeting stressed practical limitations. Attlee insisted that the annex's claims were not supported by British planning and highlighted competing obligations in places such as Greece, Palestine and Indonesia. Military and diplomatic records from the period show British and U.S. leaders were rapidly adjusting to postwar commitments, demobilization pressures and the political complexities of Soviet control in Eastern Europe.
The file has drawn renewed attention to how quickly wartime cooperation between Western Allies and the Soviet Union unraveled after 1945. Some commentators cited by the Daily Mail, including historian Damien Lewis, said the annex — whether accurate in its particulars or not — illustrates the depth of Western concern at the time about Soviet strength and intentions. The archival notes themselves make clear that senior British ministers treated the Swiss paper as intelligence in need of scrutiny rather than as an operational plan to be adopted.
The episode also underscores the transition from conventional to nuclear-era strategic thinking. Churchill is recorded in the notes as wanting Britain to possess an atomic capability and saying that if the United States would not provide such weapons the United Kingdom should develop them. Britain subsequently pursued its own nuclear programme and conducted its first atomic test in 1952.
Archivists and historians caution that the provenance and reliability of intelligence summaries and foreign assessments vary, and the presence of a document in Swiss files does not prove Allied intent to carry out the actions it described. The November 1946 meeting record, preserved in British files, reflects both the anxieties of early Cold War diplomacy and the sceptical response of Britain's postwar government to sensational intelligence claims.
The Swiss annex as reported in the newly publicised files remains an important archival artifact for scholars studying the early Cold War, illustrating the contested intelligence environment and the debate within Western capitals over how to respond to Soviet influence in postwar Europe.