The Rules of Engagement normally work effectively, when the war occurs in accordance to the existing norms and rules, i.e. when two opposing parties confront each other in a large scale war and when the opposing parties have relatively equal military power. In addition, the Rules of Engagement imply a strong ideological background of the war that means that the war is justified by reasons which are close to minds and souls of the participants of the war. In this regard, the War in Vietnam was different from traditional wars the US had even been involved in. This is why the Rules of Engagement did not always work effectively at different levels of the US army and chain-of-commandment.
At the lowest level, soldiers in the battlefield could hardly adequately understand reasons and purposes of the war. Ordinary soldiers perceived the war rather as a sort of slaughter than the struggle of the US army for the liberty of Vietnamese people or safety of the US nation. Instead, they confronted the invisible enemy, who attacked suddenly and used the tactics of the guerilla war, while officers could not explain their soldiers what they should fight for. As a result, American soldiers viewed the war in Vietnam as purposeless and useless that undermined the Rules of Engagement’s principles.
As for battalion commanders, they were in a similar position as the American soldiers because they simply got orders from their commandment and executed them blindly. In actuality, they did not have many opportunities for the adequate analysis of the orders and the proper use of the Rules of Engagement. The tactics of the large scale bombardments used by the US army made the functions of battalions unclear in terms of the overall strategy of the war since battalions did not confront the enemy in the open struggle, but struggled with guerillas.
At the same time, division commanders were more concerned with the actual purposes and strategy of the war since they have clear goals to achieve and they knew what their division should do in order to win the war. On the other hand, in the course of the war, as the US failed to gain the total control over Vietnam, division officers grew disappointed and simply got used to their failure to meet the goals defined by their commandment.
In this regard, division commanders have a similar view on the war as General William Westmoreland had. The latter adequately perceived the Rules of Engagement and he was conscious of the fact that his ultimate goal is to win the war using resources available to him. At the same time, he could not fully understand the reason for the war, at least, at the local level, in terms Vietnam. In actuality, it was Secretary of Defense Robert McNamara, who understood that the War in Vietnam was strategically important to the US in terms of the strategic US-Soviet opposition in the Asia-Pacific region.
As for the President, Lyndon Johnson definitely perceived the war as a part of the strategic opposition between the US and the USSR in the Cold War. He understood reasons and goals of the war, but the chain-of-commandment definitely failed to convey the reasons and goals of the war to lower levels, especially soldiers.