A Google Books search finds mentions of "leading from behind" starting in 1960, but none of the earliest matches present the phrase as referring to a military tactic of following soldiers into battle in order to shoot unenthusiastic participants on one's own side.
The earliest Google Books match for "lead from behind" in fact involves church leadership at a university. From The Christian Scholar, volume 42 (1960) [combined snippets]:
There is an inherent tendency throughout the Church for the minister to give his leadership from the front of the group instead of from amongst his people. In the University Pastor's situation the pressure is somewhat different. He is under pressure, because of an inherited pattern of working, to lead from behind. He is expected to be a group worker and resource person and ends up being a behind the scenes manipulator and an advisor to committee chairmen—the administrator of a program of activities.
The next-earliest match, from four years later, however, seems to view leading from behind" as a way of not sharing the same level of danger and privation as one's subordinates. From Walkabout, volume 30 (1964) [text not shown in snippet window]:
He never led from behind, nor pushed them. “He would never,” says Charles Laseron, who was a member of the first Australasian Antarctic Expedition, “expect anyone to do anything he wouldn't do himself.”
A later text specifically discusses "leading from behind" in the context of military generalship and the safety of commanding troops from a safe distance. From Country Life, volume 182 (1988) [combined snippets]:
If Alexander led from the front, and Wellington from the middle, Grant (while still exposing himself to danger) led from behind, though nothing like so far behind as the chateaux generals of the First World War. By 1939, armies were directed from even greater distances. The commander was not necessarily in the same country as the battle. Hitler was not only behind the lines, he was beneath the ground.
By 1994, however, "leading from behind" was being promoted as "a positive, non-controlling and cooperative approach" to leadership. This inclusive and non-self-promoting form of leadership is the one that most people today associate with the phrase, especially after Barack Obama adopted it to describe aspects of his administration's Middle East policy.
Now that the phrase has become famous in connection with a particular leadership style, people may be inclined to revisit it with an eye toward its applicability to other tactics and strategies (such as the battlefield executions approach cited in the OP's post). But I didn't find any evidence that the phrase was widely understood in this particular way prior to the twenty-first century.
