Showdown in the Ozarks: A Defeat From Which the Confederacy Never Recovered At snowy, muddy Pea Ridge, Arkansas, just across the border from Missouri, Union and Confederate forces met to decide the fate of the “Show Me” State. Here's What You Need to Know: The disastrous impact of Pea Ridge on Confederate fortunes was immense. For three weeks in February 1862, Union Brig. Gen. Samuel Curtis led his Army of the Southwest on a 200-mile advance southward across the Ozark plateau in Missouri and into northern Arkansas. The February weather made for abysmal campaigning, pelting the men with snow and alternately freezing the primitive dirt roads or flooding them with mud. The advance was of such vital importance to the Union cause that Curtis’s department commander, Maj. Gen. Henry W. Halleck, ordered it to proceed despite the terrible weather. Halleck was committed to a series of grand river offensives aimed at striking into the heart of Confederate Tennessee. However, as long as Rebel forces lurked in southern Missouri within range of the vital base of St. Louis, any Union gains in Tennessee would be untenable. Halleck ordered Curtis’s army to advance through Missouri and drive out the Confederate forces, securing St. Louis as a forward staging base.