Many Generals have failed to take the opportunity when it was offered; Hannibal himself was one of them. But in most of the cases there have been strong reasons for the hesitation in pursuing. After a long and fiercely-contested battle, both sides are exhausted; and there may be no fresh troops at hand to carry out the pursuit. There may be heavy rains, making the road impassable; there may be a lack of mounted troops. Most of Wellington’s victories in the Peninsular War were so dearly bought that his troops were far too exhausted themselves to think of pursuing the enemy. After Malplaquet Marlborough’s army was in no condition to follow up the victory, and the French were able to retreat in fair order and unmolested. After Spicheren, the Prussians were too exhausted to pursue, and the French withdrew in security. But after Ligny Napoleon should have pursued, at least at daybreak on the 17th. It has been shown that he had a strong force of cavalry, as well as Lobau’s Corps, available for the pursuit, and with these he could have driven Thielemann from Sombreffe. His cavalry would have threatened the Prussian flanks and rear, while Lobau’s infantry would have attacked in front. During the night it was perhaps unwise and unsafe to pursue, owing to Thielemann’s firm front, and to the enormous risks of a pursuit by night. No one knew better than Napoleon the value of pressing hard on a vanquished foe, and it is impossible to explain why he spent the morning of the 17th in trivialities. A day later, and he himself realised the position of a defeated general closely and mercilessly pursued by the victors. Grouchy cannot be blamed for failing to pursue the Prussians on the night of the 16th. He was directly under the Emperor’s orders, and he only received his independent command on the morning of the 17th. At 11 P.M., on the night of the 16th, he had been ordered to send Pajol and Excelmans in pursuit of the Prussians at daybreak, but no direction was given to him. And when it was found that Thielemann’s men still held Sombreffe, the cavalry took no further action that night. Blucher, on the 18th, found it possible to pursue the French with the utmost vigour by night; but there was this difference between the two cases--the French were totally defeated in battle, and demoralised, while the Prussians, at Ligny, were only partially defeated, and their left wing was firm and unbeaten. It was on the 17th that Grouchy’s mistakes began, after he had received his new command from Napoleon, at 11 A.M.