The Oster conspiracy of September 1938 is a coup plan conceived at the brink of war: Hans Oster and his collaborators intend to arrest Adolf Hitler before he can order the invasion of Czechoslovakia. Its central predicament is that the conspirators believe they have the men and weapons to seize Hitler, but cannot openly make the first move without risking the support of the Army on which the operation depends. When mobilisation is postponed, the plan’s narrow opportunity collapses, and its participants redirect their efforts toward stopping an agreement at Munich.

Causes and Stakes

The immediate crisis is a threatened invasion. Neville Chamberlain tells the Chiefs of Staff that the British government had hoped for an orderly transfer of the Sudeten territory to Germany, subject to a plebiscite, and that the Czechoslovak government had agreed to that arrangement. But Hitler has refused to wait even a week and has announced that German forces will invade on Saturday. Sir Horace Wilson has warned him privately that Britain will have to support France if France fulfils its treaty obligations to Czechoslovakia. Hitler’s response, as relayed to Chamberlain, is that he is prepared for every eventuality and expects Europe to be at war by the following Monday.

The political and military choices are compressed by the deadline. Chamberlain asks whether Britain would have to mobilise before Germany if it wanted to be operational by 1 October. The answer is that it would have to act that day. Partial mobilisation might demonstrate that Britain is prepared to fight and make Hitler reconsider, but Chamberlain fears that a public show of resolve could instead provoke a leader who cannot tolerate losing face. The discussion establishes the crisis’s double bind: a warning may deter Hitler, but it may also accelerate the war the conspirators hope to prevent.

The Conspirators’ Plan

The conspiracy takes shape in a private meeting at a villa at No. 9 Goethe Strasse in Berlin. Paul von Hartmann is admitted after identifying himself as being from the Foreign Ministry; General Ludwig Beck is waiting inside. Beck explains that he resigned as Chief of the General Staff a little under six weeks earlier, protesting the plan for war with Czechoslovakia. He had agreed to Hitler’s request not to make the resignation public, but remained in contact with former colleagues in the high command. He believes that if Hitler orders mobilisation the next day, the Army may disobey and move against the regime.

Hans Oster treats Beck’s disclosure as a change in the situation and argues that the conspirators must be ready to act decisively. The proposed first move is the arrest of Hitler. Beck describes the institutional obstacle: the German Army has sworn an oath of loyalty to the Führer, so it cannot openly initiate an attack. It could, however, enter the Chancellery to restore order if a disturbance began there. In Beck’s formulation, the Army’s first move must therefore appear to be a response to events set in motion by others.

Hans Oster and Captain Friedrich Heinz have worked out the operation’s practical scale. With surprise and a guarantee that the Army will protect the conspirators from an SS rescue attempt, they estimate that about fifty men will suffice to arrest Hitler. Heinz says the men are already available: experienced fighters prepared to move the next day. The Abwehr will issue weapons and provide safe houses near Wilhelmstrasse. Heinz adds that each man is personally known to him and reliable; his own experience includes fighting with Kapp in 1920 and serving with the Stahlhelm. The plan is not an abstract appeal for resistance but an attempt to assemble a small force, position it near the centre of government, and exploit surprise before the Army has to choose a side.

Decision and Conditional Violence

The conspirators do not regard the arrest itself as the end of the problem. Hans von Dohnányi asks what they should do with Hitler, and the group confronts the question of whether it can agree on his fate before knowing whether it can reach him. Hans Oster insists that other constitutional questions must wait: the immediate priority is to prevent Hitler from issuing the mobilisation order. If Hitler submits to custody, they will take him alive; if he appears likely to escape, Oster argues that they will have to shoot him. Paul von Hartmann is the first to assent. The others follow, with Beck agreeing only reluctantly.

That decision gives the plan a stark order of priorities. The conspirators defer any settlement over the form of government after the Third Reich, because they regard the impending mobilisation as the urgent danger. Their agreement is conditional rather than a settled programme for Germany’s future: first stop the order, then deal with what follows. Once they decide to strike the next day, they leave the house at intervals to avoid attracting attention. Hartmann departs first, exchanging brief handshakes and a quiet farewell with the others. Against the ordinary quiet of the sleeping suburban street, the violence they have authorized seems almost unreal to him; he tries to grasp that Hitler might be dead within a day.

The Lost Window and the Munich Turn

The conspiracy’s chance depends on timing, and diplomacy changes that timing. At two minutes past two, Sir Nevile Henderson telephones Neville Chamberlain’s party from Berlin with news that Hitler has received a message from Benito Mussolini, delivered by the Italian ambassador. Mussolini assures Hitler that Italy will stand by Germany in a conflict but asks him to postpone mobilisation for twenty-four hours so the situation can be reconsidered. Hitler agrees. The delay interrupts the conspirators’ intended sequence: their opportunity had depended on Hitler issuing the mobilisation order and the Army responding to it, while the army chief was still deciding what to do when the postponement arrived.

The conspirators later face the consequences directly. Hans Oster says that everything had depended on Brauchitsch, who was still making up his mind when Hitler postponed mobilisation. Hans Bernd Gisevius voices the group’s resulting weakness: without the Army, they are only civilians waiting while Germany is destroyed. Hartmann proposes the remaining course he can see: prevent an agreement from being signed at Munich. Erich Kordt considers that unlikely, since the British and French have already offered Hitler what he wanted and the conference may amount to little more than a public formality. Hartmann counters that the postponement is not a cancellation of mobilisation. The coup plan has not delivered the Army’s intervention; the conspiracy shifts from arresting Hitler to obstructing the diplomatic outcome that might secure his demands.

Significance in the Crisis

The plot’s defining weakness is also its source of tension. Beck’s information makes an Army revolt conceivable, but not certain; the oath of loyalty prevents the Army from being the first mover, while the conspirators’ proposed force can act only if the Army then protects it. Even the estimate of fifty men presupposes surprise and military cover. The plan is thus caught between a concrete operational design and an unresolved political commitment from the institution it needs most.

The shifting deadlines expose how vulnerable that design is to events outside the conspirators’ control. Hitler’s invasion threat makes immediate action seem necessary; Chamberlain’s debate over partial mobilisation shows that a signal of resolve might either deter or provoke him; Mussolini’s request for a twenty-four-hour pause then removes the particular trigger around which the Army’s decision had been expected to turn. In the novel, the conspiracy is not presented as a completed seizure of power but as an urgent, conditional attempt that loses its opening and must find another way to resist Hitler’s advance.