Colonel Sibley pushed on with his forces, sending in advance a cavalry detachment, which reached and relieved Fort Ridgely on the 27th of August, after it had been besieged for nine days. He himself arrived at that post with the remainder of his troops on the following day. On the 31st, he sent out a detachment of two companies, one mounted, a fatigue party of twenty men, and seventeen teams and teamsters, to reconnoitre the neighboring settlements and to bury the dead. They proceeded to the Minnesota river opposite the Lower Agency, and found and buried sixteen corpses the first day. The next day they continued their search, finding and burying fifty-four. That night they encamped on the open prairie, near the upper timber of the Birch Coolie creek, three miles from the Lower Agency. At about four o'clock of the next morning, September 2, one of their sentinels shouted, "Indians!" and almost immediately, a shower of balls rained upon the camp. From this first fire, and during the confusion attending it, the detachment suffered severely. They soon, however, gained the shelter of their wagons, and from behind them and the piles of dead horses which literally covered the ground, they returned a vigorous fire upon their assailants, meanwhile digging a rifle pit as they fought. It was a fierce morning's battle, and the foe, in largely superior numbers, had nearly surrounded and captured them when reenforcements arrived. So hot was the attack, that one of the tents was found to have one hundred and forty bullet holes through it. The boldness and severity of this attack, demonstrated to Colonel Sibley the necessity for an increase of force and very cautious movements, and accordingly he fell back to the neighborhood of Fort Ridgely. Anxious also to obtain the release of the white prisoners in Little Crow's camp, and fearing that if he won a decided success in battle they would be murdered, he determined to resort to negotiation. He therefore wrote the following note and left it fastened to a stake, on the ground where the last battle had taken place: 'If Little Crow has any propositions to make to me, let him send a halfbreed to me, and he shall be protected in and out of my camp. H. H. SIBLEY, Col. Com. Military Expedition.'