The leak of Hitler’s Case Green directive is the moment an apparently anonymous delivery gives British officials a German military document describing a planned attack on Czechoslovakia. Delivered to Hugh Legat at home and examined by Sir Alexander Cadogan, it links Hitler’s public threats to a dated, operational plan. The document strengthens the case that the danger is real, but leaves its own route into British hands—and the reason Legat was chosen—unresolved.

Crisis and the document’s arrival

The leak occurs against a rapidly narrowing diplomatic timetable. Neville Chamberlain tells his ministers and the Chiefs of Staff that Britain and the Czechoslovak Government had hoped for an orderly transfer of the Sudeten territory to Germany, subject to a plebiscite. Hitler has rejected even a week’s delay and announced that he will invade on Saturday. Sir Horace Wilson has warned him that, if France fulfils its treaty obligations to Czechoslovakia, Britain will be obliged to support France. According to the British ambassador in Berlin, Hitler has answered that he is prepared for every eventuality and expects war by the following Monday if France and Britain strike.

The government’s discussion of partial mobilisation shows the dilemma surrounding that deadline. Chamberlain recognises that mobilisation would mean Britain moving before Germany; his advisers argue that a partial measure might demonstrate resolve and make Hitler reconsider. Chamberlain, however, fears that a visible challenge could push Hitler into war, particularly if Hitler cannot tolerate losing face. The question is not simply whether Britain will fight, but how its preparations will be read. Against that uncertainty, the later arrival of the directive supplies evidence of German preparations more concrete than another diplomatic threat.

At home, Legat sees a small car stop outside while he is packing. A figure in a hat and dark coat leaves the house and gets back into the waiting vehicle. Legat reaches the front door too late to catch the car as it turns into Great Peter Street; an envelope has been left on the doormat. His name is misspelt as Leggatt, and the stationery looks official. Before removing the papers, he peers into the envelope and makes out the typed heading, Berlin, 30 May 1938. The dated document has arrived without a messenger willing to identify themself or explain its purpose.

Examination at the Foreign Office

Within ten minutes, Legat is on his way back to the office. London bears visible signs of the crisis: motorists queue for fuel, a candlelit peace vigil is under way at Westminster Abbey, and newsreel cameras illuminate the crowd outside Downing Street. By the time he reaches Number 10, the ministers have already gone through to the Cabinet meeting. He takes the five typewritten pages instead to Cadogan, the Permanent Under-Secretary at the Foreign Office.

Cadogan initially reacts with irritation at another urgent interruption. The first line is in German and begins by placing the document under the authority of the Supreme Commander of the Wehrmacht; the final page bears the signature of Lieutenant Colonel Zeitzler of the General Staff. When Legat identifies it as a directive from Hitler, Cadogan sits bolt upright. The physical markers—the formal heading, the military classification and the staff officer’s signature—give the papers an official appearance, but Cadogan still tests whether they are genuine rather than accepting them on appearance alone.

Legat can offer no accompanying message: the papers were put through his letterbox about half an hour earlier, and nothing else was delivered. Cadogan clears space on a table and reads the document closely, turning each finished page over and placing it neatly to his right. His German is good, and his previous service at the embassy in Vienna during the summer of 1914 gives him a specific historical association with the European crisis of that earlier year. His careful reading makes the document’s contents, rather than the mysterious delivery alone, the basis for the judgment that follows.

What Case Green reveals

The directive is titled War on Two Fronts with Main Effort in the South-east, Strategic Concentration ‘Green’. It describes an operation against Czechoslovakia, not merely a diplomatic contingency. The instructions call for a situation to be created within the first two or three days that would show intervening states the hopelessness of the Czech military position. German formations capable of rapid deployment are to break through the frontier fortifications quickly and boldly, with the main mobile force to follow as soon as possible. The language presents speed and the defeat of Czechoslovakia’s capacity to resist as operational objectives.

The date makes the document especially consequential: it was drawn up on 30 May, months before the current ultimatum. Cadogan reads the statement that Hitler has made an unalterable decision to destroy Czechoslovakia by military action in the near future. He recognises its close resemblance to what Hitler has told Sir Horace Wilson that morning. That correspondence offers a separate point of comparison between the secret military text and Hitler’s current words, supporting Cadogan’s conclusion that the document appears genuine.

The leak therefore changes the status of the threat without removing uncertainty. Cadogan says that Britain has already been approached during the summer by opponents of Hitler who claimed they might overthrow the Nazi regime if Britain stood firm over Czechoslovakia. He describes them as an incoherent collection of disaffected diplomats and aristocrats who want to restore the monarchy. This is the first specific material they have received from that opposition, but the directive does not identify the person who passed it on. Cadogan asks not only who supplied it and why, but why it was sent specifically to Legat. Legat cannot answer, and experiences his possession of the papers as a troubling compromise of loyalty.

Significance within the crisis

The document’s force lies in the contrast between a secret, dated military order and the shifting public language of negotiation. Before the leak, Britain is weighing whether visible preparations might deter Hitler or instead accelerate the conflict. The directive gives that debate a more definite object: an invasion plan with assigned military aims and an emphasis on speed. It does not itself settle what Britain should do, establish who leaked it, or prove that Hitler’s timetable cannot change. It does make the threat harder to treat as rhetoric alone.

Events reported later preserve that uncertainty about timing while reinforcing the pressure. In a telephone call from Berlin, Sir Nevile Henderson tells Legat that Benito Mussolini has sent a message promising that Italy will stand by Germany in a conflict, while asking Hitler to postpone mobilisation for twenty-four hours; Hitler agrees. At a later briefing, Wilson reports that Hitler has demanded a settlement by Saturday, threatening to march in otherwise, and has watched his watch as the pause in mobilisation approaches its end. The brief delay does not erase the military directive. Instead, the leak and the continuing deadlines make the crisis legible as both a negotiation and a race against an invasion plan already committed to paper.