D’Erlon’s error was his inaction when he arrived on the field, and not so much his diversion from Ney’s orders. He must have known that he could not return to Quatre-Bras in time to be of any service; but that by following up Marwitz, and falling on the rear of the Prussian right wing, he would be most likely to render the very greatest assistance to Napoleon. How he could have failed to realise the importance of his presence at such a juncture surpasses all imagination. The very fact that Marwitz’s Brigade had been able to present some show of compactness before Jacquinot’s Cavalry might have proved to him that there was still a stout resistance to be expected on the part of the Prussians. Again, we think Napoleon should have sent instructions as to how d’Erlon should act, by his aide-de-camp, in the event of the strange column being French. Had d’Erlon remained on the left wing to assist Ney, Quatre-Bras might have been won by the French. Had he realised the uselessness of a return march to Ney when he was yet at hand to help Napoleon, and thrown all his weight into the struggle at Ligny, he would have been of the greatest use in overwhelming the Prussians. Such mistakes as these are unexpected, and therefore happen, in war. CHAPTER II THE THIRD PRUSSIAN CORPS AND GROUCHY’S FORCES The Third Prussian Corps, commanded by Lieut.-General Thielemann, entered on the campaign of 1815 with a total strength of 23,980 men and 48 guns. There were four divisions[3] of infantry, containing from six to nine battalions each. These were composed as follows:-- NINTH DIVISION--Major-General BORCKE-- Battns. Men. 8th and 30th Regiments of the Line 3} 6,752 1st KURMARK Landwehr Regiment 6} TENTH DIVISION--Colonel KAMPFEN-- 27th Regiment of the Line 3} 4,045 2nd KURMARK Landwehr Regiment 3} ELEVENTH DIVISION--Colonel LUCK-- 3rd and 4th KURMARK Landwehr Regiments 6 3,634 TWELFTH DIVISION--Colonel STULPNAGEL-- 31st Regiment of the Line 3} 6,180 5th and 6th KURMARK Landwehr Regiment 6} -- ------ TOTAL Infantry 30 20,611 The cavalry numbered 2,405 men, in two brigades, as follows:-- RESERVE CAVALRY--General HOBE. Colonel MARWITZ’S Brigade-- Squadrons. Men. 7th Uhlans 3} 8th Uhlans 4} 925 9th Hussars 3} Colonel Count LOTTUM’S Brigade-- 5th Uhlans 3} 7th Dragoons 5} 1,480 3rd KURMARK Landwehr 4} 6th KURMARK Landwehr 4} -- ------ TOTAL Cavalry 26 2,405