The military resistance against Hitler increased in the meantime (early 1943). A group of young officers headed by Generalmajor Henning von Tresckow planned to assassinate Hitler and seize power. By eliminating Hitler they intended to end the two front war. They wanted to achieve this goal by reaching an agreement with the western Allies, so the war in the east could be continued.
The resistance group within the Abwehr also played an important part in this scheme. In preparation for the overthrow Admiral Canaris and his staff, among them Hans Dohnanyi, flew to Smolensk on March, 7th , 1943. Officially it would be a large meeting between the intelligence officers at the front. During these discussions however plans were made for a coup d’état. Codes for instance were agreed upon. The plan they made contained some serious flaws however. For example there was no clear plan of action regarding the isolation of the Wolfsschanze (headquarters of Hitler in Rastenburg, East Prussia) in order to prevent any counter measures to be initiated from there. The most important challenge for the conspirators was getting close enough to Hitler though.
Two attempts were made. The first one took place on March, 13th ,1943. A time bomb disguised as a bottle of liquor was smuggled aboard Hitler’s airplane. As the temperature during the flight was far below zero, the bomb did not explode. The next try was a suicide assassination. The plan was that Kolonel Rudolph-Christoph von Gersdorff would blow himself up during a visit by Hitler and other Nazi leaders to a weapons exhibition in Berlin. Hitler left the building earlier than expected however, which did not leave the colonel sufficient opportunity to explode the bomb. Efforts to assassinate Hitler were postponed for the time being, as there were no more opportunities.
Meantime at the R.S.H.A., suspicions had risen about the role of the Abwehr in the conspiracy. In April 1943, Dietrich Bonhoeffer and Hans von Dohnanyi were arrested. Hans Oster was under increasing suspicion as well and placed under house arrest.Dismissal
On February 11th , 1944 Canaris was fired as chief of the Abwehr. The many mistakes that had been made, the defection to the Allies by an agent in Istanbul and the increasing amount of inaccurate intelligence were the main reasons. The definitive straw that broke the camel’s back however was a bomb attack which was carried out on a British freighter by an Abwehrkommando in Cartagena in Spain. Hitler had prohibited such attempts as they were detrimental to the relationship with the Spanish government. When he was told that nonetheless an attack had taken place again, he was outraged and he ordered Canaris to be dismissed and the department Ausland (intelligence abroad) of the SD and the Abwehr be merged into an umbrella secret service. Heinrich Himmler and Ernst Kaltenbrunner (Bio Kaltenbrunner) were charged with this operation (Kaltenbrunner was Heydrich’s successor who had been killed on June 4th, 1942, as a result of an attack by the Tsjech resistance in May 1942). All this would finally lead to a complete dismantling of the Abwehr from mid 1944 onwards.
After his dismissal Canaris was placed under house arrest in Lauenstein Castle in the Frankenwald. On March 10th, 1944 he was discharged from active service by Grossadmiral Karl Dönitz (Bio Dönitz). It is remarkable that Canaris nevertheless was awarded the Deutsches Kreuz in Silber (German Cross in silver ) for services rendered.
In June 1944 Canaris was recalled into service, in the rank of Admiral zur Verfüging (admiral on stand-by) On 1 July, 1944, he was appointed chief O.K.W. Sonderstab für Handelskrieg und Wirtschaftliche Kampfmassnahmen (O.K.W. special staff for trade war and economic war measures, H.W.K.). This department had originally been created to fight the economic boycott of Germany by the Allies. In 1944 the HWK was hardly engaged in anything anymore because of the precarious situation Germany found itself in; its staff consisted of just a handful of people.