The most important centre of opposition to the regime within the state apparatus was in the intelligence services, whose clandestine operations offered an excellent cover for political organisation. The key figure here was Colonel Hans Oster, head of the Military Intelligence Office from 1938, and a convinced anti-Nazi as early as 1934. He was protected by the Abwehr chief, Admiral Wilhelm Canaris. Oster organized an extensive clandestine network of potential resisters in the Army and the intelligence services. He found an early ally in Hans-Bernd Gisevius, a senior official in the Interior Ministry. Hjalmar Schacht, the governor of the Reichsbank, was also in touch with this opposition.
As early as 1936 Oster and Gisevius came to the view that a regime so totally dominated by one man could only be brought down by eliminating that man – either by assassinating Hitler or by staging an Army coup against him.
In May 1938 the Army leadership was made aware of Hitler’s intention of invading Czechoslovakia, even at the risk of war with Britain, France and/or the Soviet Union. The Army Chief of Staff, General Ludwig Beck, regarded this as not only immoral but reckless, since he believed that Germany would lose such a war. Oster and Beck sent emissaries to Paris and London to advise the British and French to resist Hitler’s demands, and thereby strengthen the hand of Hitler’s opponents in the Army.
Writing of the 1938 conspiracy, the German historian Klaus-Jürgen Müller observed that the conspiracy was a loosely organized collection of two different groups. One group comprising the Army’s Chief of Staff General Ludwig Beck, the Abwehr chief, Admiral Wilhelm Canaris, and the Foreign Office's State Secretary, Baron Ernst von Weizsäcker were the "anti-war" group in the German government, which was determined to avoid a war in 1938 that it felt Germany would lose. This group was not committed to the overthrow of the regime but was loosely allied to another, more radical group, the "anti-Nazi" fraction centered on Colonel Hans Oster and Hans Bernd Gisevius, which wanted to use the crisis as an excuse for executing a putsch to overthrow the Nazi regime.[10] The divergent aims between these two factions produced considerable tensions
In August Beck spoke openly at a meeting of Army Generals in Berlin about his opposition to a war with the western powers over Czechoslovakia. When Hitler was informed of this, he demanded and received Beck’s resignation. Beck was highly respected in the Army and his removal shocked the officer corps. His successor as Chief of Staff, Franz Halder, remained in touch with him, and was also in touch with Oster. Privately, he said that he considered Hitler “the incarnation of evil.”[12] During September, plans for a move against Hitler were formulated, involving General Erwin von Witzleben, the Army commander of the Berlin Military Region and thus well-placed to stage a coup.
The outbreak of war made the further mobilization of resistance in the Army more difficult. Halder continued to vacillate. In late 1939 and early 1940 he opposed Hitler’s plans to attack France, and kept in touch with the opposition through General Carl-Heinrich von Stülpnagel, an active oppositionist. Talk of a coup again began to circulate, and for the first time the idea of killing Hitler with a bomb was taken up by the more determined members of the resistance circles, such as Oster and Erich Kordt, who declared himself willing to do the deed. At the Army headquarters at Zossen, south of Berlin, a group of officers called Action Group Zossen was also planning a coup.
When in November 1939 it seemed that Hitler was about to order an immediate attack in the west, the conspirators persuaded General Wilhelm Ritter von Leeb, commander of Army Group C on the Belgian border, to support a planned coup if Hitler gave such an order. At the same time Oster warned the Dutch and the Belgians that Hitler was about to attack them – his warnings were not believed. But when Hitler postponed the attack until 1940, the conspiracy again lost momentum, and Halder formed the view that the German people would not accept a coup. Again, the chance was lost.