According to Gisevius's book - I can't recall the title - there was a plot to overthrow him as late as late as November 1939. The generals were apparently really concerned about the planned invasion of France, but the delay until May 1940 ended up softening their stance on Hitler, much to Gisevius's annoyance. The theory amongst the anti-Nazis in the General Staff was that Germany would quickly be beaten by France, removing the need for them to get their own hands dirty in politics.All this is absolutely true. The military had the power to topple Hitler at least right until the successful invasion of Czecoslovakia. They chose instead to back the nazis. The change of the oath was made by Blomberg, who at the time (night of the long knives) was powerful enough to force Hitler to sacrifice the armed branch of the nazi party in order to appease the military, represented by Blomberg.
There was also the matter of the purge of the military following the Blomberg-Fritsch Affair in January 1938. Many of the more anti-Hitler officers were removed from the centres of power, whereas strong pro-Hitler officers such as Keitel were either promoted or moved into positions that made them more of an obstacle to potential conspirators. Hitler also took direct control of the military after that date, and even the anti-Nazis were comfortable with that, because the other two contenders were Goering and Himmler. Most of the military despised Himmler, though they might have tolerated Goering.Also true. I would only change "disdain of practical politics" to "disdain of diplomacy" when caution collied with Hitler's fixed idea of a conspiracy against Germany.
That Hitler succeeded in seizing power and starting wars that even the german generals were hesitant about is because he was carrying on very popular ideas among the german people and especially its ruling elite. The disagreements were not about conquering lebensraum, they were about where, when, and who to do it.
Too bad Goebbels' suggestion of installing Beck as Chief of the OKW didn't work out. Could have solved a lot of problems for the world.