On appropriations, General Walker, Chief of Army Finance, to a Congressional committee in 1924:
I think it would. I think when the budget has once been approved by the President and transmitted to Congress, it is his budget estimate and no officer or official of the War Department would have any right to come up here and attempt to get a single dollar more than…contained in the estimate.
On allegiance, General George Marshall on loyalty to the President and not Congress in 1940:
I submit to you…the impossibility of developing an efficient army if decisions which are purely military in nature are continually subjected to investigation, cross examination, debate, ridicule, and public discussion by pressure groups, and by individuals with only a superficial knowledge of military matters, or the actual facts in the particular case. I submit that there is a clear line of demarcation between the democratic freedom of discussion which we are determined to preserve and a destructive procedure which promotes discontent and destroys confidence in the army.
On oversight, Admiral Nimitz testifying during the National Security Act hearings in 1946:
Senator, it is my impression that the Constitution of the United States charges the Congress with the furnishing of armed forces. It charges the President with their use.
The Congress, in the furnishing of the armed forces, is entitled to every bit of information that it needs, and I perceive no objection whatever in the writing into this bill of the kind of safeguards you have in mind; because it is the Congress that makes provision for the armed forces and they should certainly have the right to every bit of information that they think they need in making appropriations.
Secretary of Defense Robert Gates at the Naval Academy commencement in 2007:
As officers, you will have a responsibility to communicate to those below you that the American military must be non-political and recognize the obligation we owe the Congress to be honest and true in our reporting to them. Especially when it involves admitting mistakes or problems.
Source for the first three: The Pentagon and the Presidency
After reading these quotes, consider Congressional pressure on the Navy, the Air Force, and more.