Several First World War probing attacks could advance at once, with reserves supporting whichever approach made the best progress. This left the choice of where to commit further resources open until results were visible. The comparison is with deciding in advance that one attack is the main effort and another merely a diversion. It illustrates a commander's ability to respond to progress without committing everything to the initial assumption.
Notable Point · 3:29:33-3:30:09
Several probing attacks and reserves behind the successful one
The institutional-learning argument uses simultaneous probes as an analogy for keeping alternatives open.