HEADQUARTERS SOUTHWEST EXPEDITION,
Springfield, Mo., July 12, 1861.

SIR: I have the honor to inform you that I left Saint Louis Sunday, June 23, with 360 men, and arrived at Rolla, the terminus of the Southwest Branch of the Pacific Railroad, the same day, where I established a depot. I proceeded from that point the following day, and arrived at this place Monday, July 1, having established garrisons at various points along the route to keep my communications open.

After taking the necessary steps to make this my center of operations, I issued orders to Colonel Sigel and Colonel Salomon, the headquarters of whose regiments were at Sarcoxie and Neosho, to concentrate their forces and move in the direction of Carthage, where, I was led to believe from information received, Governor Jackson's and General Rains' forces were encamped. In compliance with my orders, Colonel Sigel advanced with all his force, except one company left at Neosho, to the point designated, and at about 10 o'clock in the morning of the 5th instant engaged the enemy. The enemy, being vastly superior in numbers, completely surrounded our troops and attempted to cut them off. Upon receiving information of these facts, I hastily collected about 400 men, and within three hours after receiving the intelligence was on my way to relieve Colonel Sigel's command. I fell in with the retreating column at Mount Vernon, Lawrence Conty, and prepared to give the enemy battle, who I learned from my scouts was advancing in great force. Having remained at Mount Vernon for two days, I took up my line of march for this place, fearing an attack on it from the combined forces of Jackson, Rains, Price, and McCulloch, whose troops I learned were about to form a junction on the Arkansas frontier, towards which the enemy retired from Carthage.

I have an effective force of 2,600 officers and men at this point under my command, and feel confident in my ability to hold until joined by General Lyon, who I learn is within two or three days' march of me.

I am very deficient in ammunition for the eighth field pieces attached to this command; also for the 69-caliber rifle musket with which the principal part of my command is armed. I have repeatedly presented my wants in these particulars, and pressed them upon the attention of the authorities at the Saint Louis Arsenal without effect.

The inhabitants of this portion of the country are generally loyal, and since my arrival here I have organized several regiments of Home Guards, but they are very deficient in arms and ammunition. Mounted troops are much needed. Colonel Wyman's regiment Illinois Volunteers is expected to arrive here soon.

Inclosed please find official report of the battle at Dry Fork [Numbers 2.];  also a plan of the battle.* I inclose a printed copy of a proclamation issued by me at this place on the 4th instant.+

I have the honor to be, very respectfully, your obedient servant,

T. W. SWEENY,

Commanding, Second Infantry, Commanding.