Clausewitz argues that war is politics by other means, which is true. The military does not decide when to go to war, it is the politicians. The military does not decide when to terminate war, it is the politicians. Lastly, civilians are put in charge over the military for a reason. They are responsible for funding the war--money which ultimately comes from taxpayers--and therefore it is the politician who is held accountable to the people via elections. It is the politician (sad to say at times) who is the link between the people and the military in a Democracy. When this link fails, we get a runaway war, as we did in Vietnam and in Iraq.
Now common history tells us that Vietnam debacle was the fault of the politicians micromanaging the war, as argued by Eliot Cohen in Supreme Command. Recent historical studies of the Pentagon Papers and LBJ White House records tell us the opposite. Bombing target selection is the most commonly cited form of micromanaging, but in fact almost all targets selected proposed by the Air Force were approved by the White House, without any bruising discussion! If Churchill or Lincoln were running the White House during Vietnam, as argues Cohen, there would have been tense arguments about the nano-details. And if Clemenceau were running the White House, once a week he would have been going to Vietnam to infuriate the generals running the war through detailed questioning. All of this political interest in war details would surely have made a general quit or have him fired, none of which happened in our commonly cited failed wars, Vietnam and Iraq II.
Furthermore, it is the responsibility of the politicians to take the long view, the historical view of the results of the war. When this does not happen and the politician obsequiously follows the generals, the war is short-sighted only thinking about the near-term victory, and the result is the premature finish of the first (1991) and second Gulf War (2003).