When top-level commanders attempt to run the war at the tactical level, the risk is great that they will lose the
strategic overview of the situation and get mired in the
minutiae. In the past, this was impossible, since technology did not allow the
commanding general, (or worse, the
civilian leadership and
bureaucracy) to actively direct the actions of the leadership at the
squad and
company level.
In pre-industrial times, the commanding general was forced to delegate, as the only was to get an order transmitted to the front-line foot soldier was to yell it in his ear. The general sent riders (or runners) to his field-grade commanders, who then dispatched their company-level commanders to direct the troops to complete the mission. This distinction still has an echo in the US military rank structure in that lieutenants and captains are considered company-grade officers, majors and colonels are called field-grade commanders, and generals are referred to as flag-rank. (Different from the unit or country flag, the general’s flag was carried so that the soldiers would know where the commander was. It is still used by generals today.)
In the age of sharp implements, tactics weren’t as critical as they are today, as the primary criteria was to get more guys with pointy stuff onto the field than the enemy. It wasn’t until firearms were developed that the tactical environment could be significantly altered by the acts of a dedicated group of individuals. (I know that is a generalization.) Once this became the case, the desire for the upper levels of military leadership to interfere with the decisions of the tactical command increased significantly.
The first war to truly reflect this was the Vietnam War. Not only did US senior military leadership micromanage the troops, civilian advisors and the President himself would weigh in with their opinion all the way from Washington, to the point of designating individual targets on the ground. Improved tactical communications made this possible, for even through WWII, it was almost impossible to make a radio small, light, and rugged enough to follow a single platoon into combat (special ops troops being the exception.) In addition, the increase in an individual soldier’s personal lethality enabled smaller units to be used in more creative ways, and the dynamic nature of the Vietnam War lent itself to small-unit mission mentality and remote control of tactical elements, as the generals no longer had a commanding view of the field, or even a handle on the size, shape, and location of the front. This approach didn't work very well, as the initiative of the tactical commander was lost.
This mentality has come to a head during this most recent military endeavor, the Second Iraqi War. Command decisions were made from rear-echelon command posts and the White House and transmitted almost instantaneously to the front. At this point, however, the extreme lethality of single weapon systems and their extreme accuracy enabled the military leadership to basically run the entire battle by proxy, with the American public riding shotgun in the form of embedded journalists. Luckily, the improved nature of the communications and weaponry enabled this to occur without a significant impact on tactical initiative. However, it did remove a great deal of the decision making process from local commanders.