On the night of Thursday, March 6, Confederates commanded by Maj. Gen. Earl Van Dorn set out to outflank the Union position near Pea Ridge in northwestern Arkansas. Van Dorn divided his force into two columns. Learning of the Confederate advance, the Federals commanded by Brig. Gen. Samuel Curtis marched north to Pea Ridge or Elkhorn Tavern meet it the next morning.
Compounded by the killing on March 7 of Brig. Gen. Ben McCulloch and Brig. Gen. James McIntosh, the Confederate attack ground to a halt. With assistance by three regiments of Confederate Indians commanded by Brig. Gen. Albert Pike, the Southerners held their ground. On Saturday morning, March 8, the Federals launched a massive assault on Gen. Van Dorn and his troops, and forced the Confederates to retreat across the Arkansas River. The battle was over and the Confederacy had lost Missouri, which hampered their efforts to maintain the Mississippi River. The 11,000 Federals sustained losses of 203 killed, 908 wounded and 201 missing or captured. Gen. Van Dorn’s troops numbered about 14,000 and sustained casualties of about 600 killed or wounded and 200 missing or captured.
In Virginia, President Jefferson Davis warned Gen. Joseph Johnston at Manassas and Centreville that the Federals were about to advance. He suggested that Gen. Johnston take his army and move to more defensible positions south of the Rappahannock River. The Federals under Maj. Gen. George McClellan finally left the environs of Washington on March 7, heading southwest towards Manassas. At Centreville, Gen. Johnston ordered his men to begin packing up their winter quarters.
A new type of battle broke out in Hampton Roads, near Norfolk, on the same day, when the CSS Virginia, the ironclad ship built on the hulk of the old USS Merrimac, steamed out of Norfolk Harbor under command of Flag Officer Franklin Buchanan. Three traditional wooden warships – the USS Cumberland (24 guns), Congress (50 guns) and Minnesota (40 guns) – opposed the Virginia.
The Confederate ironclad, firing all eight guns, rammed the Cumberland and forced the badly damaged Congress and Minnesota to run aground. The Cumberland, with a loss of 121 officers and men, became the first ship in the world to sink as a result of action from an ironclad vessel. It went down fighting and the Congress was burned after surrendering. Buchanan was wounded and command of the ironclad fell to Lt. Catesby ap Roger Jones. The Federal casualties were high, and the Virginia withdrew to Norfolk as darkness approached, planning to attend to the grounded Minnesota the next day.
On Sunday, March 9, the Confederate Army under Gen. Johnston pressed the short-lived Centreville Military Railroad (the world’s first railroad built exclusively for military purposes) into service for a final time, using it to abandon the camps at Centreville. Marching south from Manassas, Johnston’s troops crossed the Rappahannock River at Rappahannock Station (now Remington) and set up defensive lines towards Fredericksburg. McClellan’s army moved into the former Confederate camps two days later and found nothing of military value left behind by the Southerners.
The same day, the CSS Virginia steamed out again into Hampton Roads and encountered the newly arrived USS Monitor, an ironclad launched in New York Jan. 30; it had a single revolving turret housing two 11-inch guns. For two hours the two iron ships dueled, circling, ramming, charging and withdrawing.
Lt. John Wordon on the Monitor sustained an eye injury and command devolved on Lt. Samuel Greene. Standing helplessly by, the strong Federal wooden fleet and the wooden Confederate escort ships watched the contest. The traditional means of naval warfare – wooden ships – had just become obsolete.
The battle ended when both ironclads withdrew, neither badly damaged and neither accomplishing anything of military importance other than to establish the end of an era. Union casualties numbered 370 (121 killed on the Cumberland), Confederate losses 25. Both sides now feared new machines of war that they could not yet understand. Where Washington’s defenses might be threatened by the Virginia, so Richmond’s might now be threatened by the Monitor.