Failure to Execute - Maneuver of Smolensk

But for Neveroski's staunch resistance, the French cavalry might well have reached Smolensk by the evening of the 14th.  Under the circumstance, however, Napoleon decided, somewhat unwisely as it proved, to check his forward movement for twenty-four hours in order to regroup his forces.  It is difficult to understand this decision, as it robbed the maneuver of much of its vital surprise element and afforded the Russians with time to react, for by the early hours of the 15th both Bagration and Barclay had learned from Neveroski of the French offensive and had forthwith ordered their troops to retrace their steps to Smolensk.  The latter wasted no time in ordering General Raevski's VIIth Corps to occupy the city's defenses, and by dawn on the 15th, these troops were entering the city from the west to strengthen the garrison (commanded by Count Bennigsen); they were soon joined by Neveroski's diminished but gallant division.  Thus Napoleon missed his chance of taking Smolensk by surprise.  Fifteenth August was also the Emperor's forty-third birthday and part of the day was spent somewhat unnecessarily reviewing the army.

~D. Chandler, The Campaigns of Napoleon, p. 785