I'm about fifty pages into Franz Neumann's Behemoth: The Structure and Practice of National Socialism, 1933-1944
(1942, 1944), and I just want to note that he's already, more or less in passing, demolished the "we are simple soldiers!" defense. In talking about the Weimar Republic, he says:
The Reichswehr, reduced to 100,000 men by the Versailles Treaty, continued to be the stronghold of conservatism and nationalism. With army careers now closed to many and promotion slow, there is little wonder that the officers' corps became militantly anti-democratic, despising parliamentarianism because it pried too closely into the secrets of army expenditure, and detesting the Socialists because they had accepted the Versailles Treaty and the destruction of the supremacy of German militarism. Whenever a political crisis arose, the army invariably sided with the anti-democratic elements.
And let's not forget the role of the Reichswehr in the end of World War I and the "stab in the back" myth. The Reichswehr was intensely
involved in politics, and that was hardly a secret.
There was certainly less scope for officers to wield political power in the Wehrmacht, with the shift from a pluralist, struggling government which always stood in a suppliant relationship to the army, to a single-party dictatorship in which the army stood suppliant to the Führer, and the generals may have wanted
to be ignorant of Nazi politics, but they got there by trying to make a political deal with Hitler. The fact that the deal went so very badly for them--like any deal Hitler made with anyone, it was "heads I win, tails you lose"--is not a sign of political naivete on their part, but a sign of just how disruptive a force Hitler was in the political arena.
Liddell Hart seems to have accepted the German generals' pose as political naifs in good faith, but a pose is all it was.
Neumann, Franz. Behemoth: The Structure and Practice of National Socialism, 1933-1944
. 1942. Expanded ed. 1944. Chicago: Ivan R. Dee, 2009.