Taken from The American Heritage Picture History of The Civil War by Bruce Catton

With the border state of Kentucky safely in the Northern column after the capture of Forts Henry and  Donelson, the war suddenly swirled off to the southwest.  In Missouri, Brigadier General Samuel Curtis, with 11,000 troops, chased the Rebels from the state into northwestern Arkansas.  To meet this threat, the dashing Mississippian Earl Van Dorn assembled his scattered forces and moved north.   Curtis, a ramrod-stiff old ex-regular, was outnumbered and prudently dug in, in front of a rocky eminence known as Pea Ridge.

On March 7 [1862] Van Dorn executued a "double envelopment" - half his army stole behind Pea Ridge, marched around three-fourths of Curtis' force, and struck his left rear near Elkhorn Tavern; the other half attacked the right rear.  Curtis countered by ordering his force about-face.  The fighting was severest near the tavern, where a stubborn defense by a tough regular, Colonel Eugene Carr, absorbed repeated Confederate attacks.

Van Dorn's fancy tactics had put the enemy between him and his supply train, and now his men were hungry and almost out of ammunition.  The next day Curtis sent Franz Sigel's unblooded troops against them.   Sigel had one of his rare good days of the war, and the shattered Rebels were sent flying in all directions.   For three more years guerrilla warfare would ravage the state, but the Union grip on Missouri was now secure.