Hardinge accompanied Sir C. Stewart to the Congress of Vienna; and when the war again broke out on Napoleon's return from Elba, he was at once selected as a military and diplomatic officer on Blüchers staff, with the rank of Brigadier-General. Müffling held the corresponding post of Prussian representative at Wellington's head-quarters. Their chief duties were to act as channels of communication between the allied commanders. The Duke had here rightly estimated his officer, such duties requiring not only firmness and military knowledge but consummate tact and judgment.
On June 16th, in the early morning before the memorable battle of Ligny, the Duke of Wellington, being doubtful as to Napoleon's real intentions and considering the small French force in front of Quatre Bras to be only a feint, rode forward to the windmill of Bussy, near Brye, overlooking the position at Ligny, for the purpose of conferring with Blücher on the best plan for uniting against their common enemy. At this moment Sir H. Hardinge, who was engaged in reconnoitring the French position, saw a group of horsemen whom he at first took to be a party of the enemy. On coming nearer he observed that their horses' tails were 'docked,' and at once concluded they were English. Galloping up to the group, and trusting to the speed of his horse in the event of his being mistaken, he came upon the Duke and his staff. Then occurred a conversation, published in Stanhope's Recollections, which relates how the Duke expressed his strong disapprobation of the ground taken up by
