HEADQUARTERS ARMY OF THE FRONTIER,
Rhea's Mills, Ark., December 20, 1862.

GENERAL: I have the honor to report that, on the 2nd instant, and four days subsequent to the battle of Cane Hill, or Boston Mountain, of November 28, I obtained reliable information that the entire force of infantry and artillery of General Hindman's army had crossed the Arkansas River and joined General Marmaduke at lee's Creek, 15 miles north of Van Buren, to which point the latter had retreated after the battle of the 28th ultimo. I further learned that the united forces under General Hindman's command numbered between 25,000 and 30,000 men, and that he designed advancing upon me in case I did not attack him south of the mountains.

Determined to hold my position at Cane Hill, unless driven from it by a superior force, I immediately telegraphed to the Second and Third Divisions to come to my support by forced marches. I may here mention that I had no knowledge of the whereabouts of theses two divisions, except from rumor, and had not been apprised of their movements or locality for a period of over two weeks. My telegraphic dispatch reached General Herron, commanding the Second and Third Divisions, on the 3rd, who promptly responded to my order, keeping me advise, by telegraph from Elkhorn, of his progress. The Second and Third Brigades of the First Division, with my headquarters, were at Cane Hill; the First Brigade at Rhea's Mills, 8 miles north, where a large supply train, just arrived from Fort Scott, was halted. My pickets were advanced 6 miles beyond Cane Hill, on the road leading to Van Buren, and a strong outpost of the Second Kansas established where that road intersects the Cove Creek road, running from Fayetteville to Van Buren, and which road passes about 6 miles east of Cane Hill.

On the morning of the 5th instant, this outpost was attacked by a large force of rebel cavalry, but they were repulsed and driven back some 6 miles through the mountains. Expecting that the same demonstration would be repeated on the next morning, I directed Colonel [W. F.] Cloud, commanding the Third Brigade, to strengthen this post by the addition of 100 cavalry and two howitzers, to be at the outpost at daybreak. In consequence of this order not being promptly carried out, and the support not arriving at the time directed, the pickets, on being attacked about daylight by a superior force, were compelled to retire some 3 miles, when, support having reached them, they held the ground during the day, with continual skirmishing, in which several of my men were wounded and a number of the enemy killed.

The enemy had now got possession of the Cove Creek and Fayetteville road, and I learned about 8 p. m. that a force of about 10,000 had advanced beyond the junction of the Cover Creek road with the Cane Hill and Van Buren road, and were masse upon the mountain in front of my outpost, while the remainder of the rebel army was below the junction of the roads just named, about 3 miles in rear of their advance. The Third Brigade, under Colonel Cloud, was ordered to bivouac for the night on their arms upon the ground south of the town that I had selected to make a stand upon in case I was attacked in front.

It was now evident that a general engagement must take place next day, and my apprehensions were that with their superior numbers they would make a feint in front, while with their main force they would make a flank movement on my left, by the Cove Creek road, to intercept General Herron before he could reach me from Fayetteville, which point he was expected to reach by daylight on the morning of the 7th.