A file discovered at the UK National Archives and reported by the Daily Mail outlines an alleged British and American plan drawn up in 1946 that would have used conventional and atomic weapons to strike Soviet forces in Germany and eastern Europe.
The document, described in the file as “Annex II” and marked "top secret," was reportedly handed to Winston Churchill by a Swiss staff officer and read at a November 5, 1946, meeting in Prime Minister Clement Attlee’s Commons office. Attlee later dismissed the contents as “entirely fictitious,” according to the meeting notes.
The Swiss account, as recorded in the annex, described a two‑phase Allied counter‑attack designed to "paralyse the points of departure" of a purported Soviet offensive for 30 to 45 days. In the first phase, lasting one day, the document said Allied forces would destroy bridges, railway stations and other nodal points in a zone spanning the Elbe, Danube and Vistula rivers. A second phase of concentrated air operations would target Poland and continue tactical strikes in the first zone.
The annex named aircraft and munitions in alarming numbers: 400 Mosquito fighter‑bombers carrying up to 200 atomic bombs, backed by 4,000 heavy and medium bombers and 1,200 fighters, with additional reserves ready for several days of fighting. The Swiss noted, however, that execution of such a plan would depend on American resources and predicted Allied air forces would not be ready until June 1947.
The file was found among papers at Kew and is distinct from Operation Unthinkable, the better‑known 1945 contingency study ordered by Churchill that envisaged a conventional surprise offensive against Soviet forces immediately after Nazi Germany’s defeat. Unthinkable — drawn up in mid‑1945 and released by the National Archives in 1998 — proposed large tank formations and the re‑arming of former German units and was rejected by British military chiefs and the United States.
The newly publicised annex, by contrast, described the possible use of atomic weapons in 1947. Contemporary reality undercuts key details in the Swiss account: in the autumn of 1946 the United States possessed about nine nuclear bombs and Britain had none. Britain conducted its first atomic test in 1952 and the United States did not build a stockpile on the scale cited in the annex until later.
Records of the November 1946 meeting show Churchill read out the annex after returning from Switzerland, where he told attendees he had found the Swiss "very frightened of Russian intentions." Present were senior wartime figures including former foreign secretary Anthony Eden and General Hastings Ismay, alongside Labour ministers. The meeting notes record Churchill stressing that knowledge of the annex’s contents should be kept to a "smallest circle." Attlee, according to the notes, insisted no such plans had been worked out and argued that manpower and equipment constraints — with forces committed in Greece, Palestine and Indonesia — made execution impossible.
Historians caution that files of this type shed light on the sharp deterioration of wartime cooperation between the Western Allies and the Soviet Union but do not, by themselves, confirm operational intent. Damien Lewis, a historian quoted in the Daily Mail coverage, said the dossier illustrates how rapidly the wartime alliance frayed and noted that U.S. nuclear monopoly at the time gave Western planners a perceived, if fleeting, advantage.
The annex also included a Swiss assessment of Soviet strength in Central and Eastern Europe, citing an estimated 130 divisions and 50 armoured brigades across Germany, Austria, Hungary, Poland and the Baltic states. Swiss commentators in the document urged caution, saying they did not possess more accurate information than other foreign services and recommending "not to express any judgement" on the plan’s veracity.
British postwar political debate about nuclear weapons was already underway. According to the meeting notes, Churchill said Britain should seek about 50 atomic bombs and, if the United States would not transfer technology, should develop its own. Attlee’s government resisted U.S. pressure to share atomic design information; Britain subsequently pursued an independent programme and detonated its first atomic device in 1952.
The newly reported annex joins a body of published wartime and immediate postwar contingency studies that show Western leaders were at times prepared to contemplate a wide range of military responses to perceived Soviet expansion. Military planners and political leaders ultimately rejected large‑scale offensive operations against the Soviet Union in the immediate postwar years, and U.S. policymakers declined to support Unthinkable in 1945. The United States did commission its own late‑1946 plans — codenamed Pincher — but those proposals also differed materially from the Swiss description recorded in Annex II.
Archivists and historians will likely examine the document within the wider corpus of postwar diplomatic and military records to better understand how information circulated among Allied capitals in 1945–47 and how fear of Soviet intentions influenced planning debates. The file as described in press reports provides a stark illustration of how quickly wartime cooperation had given way to mutual suspicion that would define the Cold War era.