It was in Curtis’ army in the campaign which closed with the Battle of Pea Ridge, in which Dodge commanded a brigade, and the Fourth Regiment was under command of Lieutenant-Colonel Galligan, who was wounded in the battle and resigned, April 3d, when Adjutant J. A. Williamson was promoted to lieutenant-colonel, and Lieutenant R. A. Stitt became adjutant. The Fourth was in the thickest of the fight at Pea Ridge on both days, and did excellent service, losing nearly one-half of its entire number in killed, wounded and missing. Dodge and Williamson were among the wounded. In the first day’s battle, on the 7th of March, 1862, the Fourth Iowa, in the brigade commanded by Colonel Dodge, fought like veterans. Early in the day, General Carr ‘s Division, on the right wing of Curtis’ army, assailed by overwhelming numbers, made a most determined fight. For seven hours the Rebels pressed on his lines, and his division was forced back half a mile, while presenting an unbroken front to the enemy. The Fourth Iowa and Thirty-fifth Illinois, under Dodge, lying behind an old fence, were now attacked by a greatly superior force supported by artillery. The charge was met by a deadly fire and the enemy driven back in confusion. Again and again the Rebels rallied and renewed the attack and were each time repulsed with heavy loss. At one time the ammunition became exhausted and the Fourth made a gallant bayonet charge under the direction of General Curtis. The splendid fighting of the Fourth Iowa and Thirty-fifth Illinois challenged the admiration of General Van Dorn and other Confederate officers. For brilliant services in this battle, Colonel Dodge was made a Brigadier-General; Williamson was promoted to colonel; Captain Burton to lieutenant-colonel.

Having driven the Confederate army out of Missouri, General Curtis marched toward Little Rock. The continuous rains rendered the roads nearly impassable and after remaining at Batesville and Jacksonsport several months, and finding it impossible to subsist his army in that country, he marched to Helena. The Fourth Regiment remained at Helena until December, when it joined General Sherman’s expedition against Vicksburg and took a prominent part in that campaign, which terminated so disastrously to the Union cause.

On the 20th of December, 1862, General W. T. Sherman embarked with a large army on transports at Memphis, and, descending to Helena, was joined there by General Steele and his command. The army, which filled a hundred transports, then continued the journey to Milliken ‘s Bend, about twenty-five miles above Vicksburg. On Christmas evening orders were issued for the fleet, next day, to attack Vicksburg. The plan was for General Grant to march to the rear of the city and cooperate with Sherman in the attack. On the 20th of December, General Grant’s army was at Oxford preparing to move on Jackson and Vicksburg. He had collected at Holly Springs, arms, ammunition and provision for the army during the campaign. Colonel Murphy, of the Eighth Wisconsin, with 1,000 men, was guarding them. He was surprised by Van Dorn ‘s cavalry early one morning and, without resistance, surrendered, with all of the army supplies. This loss of his trains and supplies compelled Grant to fall back to Grand Junction, and defeated his plan of cooperation with Sherman in the attack upon Vicksburg. Grant’s retreat bad liberated the Confederate army, which had been gathered at Grenada to oppose his advance, and, unknown to Sherman, it had hastened to the defense of Vicksburg. This city occupied a range of high bluffs bounded on the north by swamps and bayous almost impassable. Protected by abatis covering rifle pits, with the bluffs as strongly fortified as skill and slave labor combined could make them, the place was absolutely impregnable from assault, when defended by a large army. The mighty task which Sherman attempted was simply impossible; but somewhere in the long line he hoped to find a weak place where the army could force its way. The men were in excellent spirits and anxious to be led against the stronghold. Porter’s gunboats were ready to render all possible assistance. The troops were landed along the Yazoo River on the 26th of December. By the morning of the 29th the entire army was in position to move upon the works. The Rebel batteries opened fire on our lines and the battle began. All night our soldiers had heard the heavily loaded trains rolling into Vicksburg, bringing reinforcements from Pemberton’s army. Thayer, who commanded the brigade in which was the Fourth Iowa, charged upon the enemy and carried the first line, drove the Rebels from the second and halted under a terrible fire, waiting for support, scores of brave men and officers falling at every discharge. The couriers, sent for reinforcements, were shot down. Thayer rode along the line, in anguish over the slaughter of his men and warmly commended their bravery. But no help came, and, at last, he gave the order to fall back. Slowly the regiment retired in order, as the terrible fire thinned its ranks.

Ingersoll says: "There were many Iowa regiments and batteries which behaved with that high degree of credit which the troops of the State everywhere maintained throughout the war, but no regiment from any State behaved with more devoted gallantry than the Fourth in the assault of the 29th of December. Every officer and man did his whole duty and only regretted that they could not accomplish more."

The regiment went into action with’ five hundred and eighty men and officers, of which one hundred and twelve were killed and wounded. Colonel Williamson and Captain Still were wounded, Lieutenant J. M. Miller and Leander Pitzer were killed. General Grant, long afterward learning of the gallant conduct of the regiment, commanded by general order that the Fourth Iowa Infantry have inscribed on its colors," First at Chickasaw Bayou." All the brave fighting and sacrifices of that bloody battle were in vain, as it was not possible for the gallant army and its able commander to take that strongly fortified city by assault, and it was an undeserved humiliation for the President to remove General Sherman from command, by placing over him General McClernand.

The Fourth Iowa was in the campaign led by McClernand against Arkansas Post and was commanded by Lieutenant-Colonel Burton, Colonel Williamson being disabled by wounds and sickness. In January, 1863, the Fourth was again in the army before Vicksburg, where, for two months, were spent the darkest days of its service in the cypress swamps, under the frowning batteries of the enemy. Toiling on the famous canal, struggling in mud and rain, lying in camp through that dreary winter, while Grant was working out the great problem of how to subdue the Rebel stronghold and open the Mississippi River. With Steele’s Division, the Fourth embarked on steamers, early in April and, ascending the river to Greenville, thence marched eastward, threatening Vicksburg in the rear and collecting great quantities of provisions for the army, while Grant was drawing his lines around the doomed city.

Returning towards Vicksburg, this division of the army rejoined the main body at Grand Gulf and took part in the brilliant campaign, which drove Pemberton’s army back into the city. The Fourth was in the assault of the 22d and met with severe loss in the general defeat; then, for forty-seven days, it was employed in the siege, as the lines were gradually closed. The regiment lost about eighty men during the siege. It was there to rejoice in the final great victory, which resulted in the capture of the stronghold and the entire Confederate army defending it, by far the most damaging blow inflicted upon the enemy up to this time.

After the surrender, the Fourth joined Sherman in his movement against General Johnston’s army, capturing Jackson, the Capital, and driving Johnson out of the State. Colonel Williamson was now in command of a brigade in which was the Fourth Iowa. The regiment was in Osterhaus’ Division in his expedition to Corinth, Iuka and Cherokee, and took part in several engagements.

In November, the division joined the army at Chattanooga. In the Battle of Lookout Mountain the Fourth was on the extreme left of Hooker’s command. When the battle opened, the division moved across an open field to Lookout Creek, where it was for some time exposed to a severe fire, but finally moved on up the mountain, where the fight was warm. As night came on, the regiment held its position on the mountain prepared to renew the battle next day. When morning dawned, it was discovered that the enemy had withdrawn to Missionary Ridge. Early in the morning, the Fourth, Ninth and Thirty-first were sent to Rossville Gap, and placed in a good strategic position, turning the Rebel left. They were attacked by a heavy column of the enemy and a fierce battle ensued in which the Fourth bore an active part until the Rebels were routed. It joined in the pursuit on the 26th, and at the Battle of Ringgold, the next day, fought with great gallantry, saving two railroad bridges, which were set on fire by the retreating army. After these battles the Fourth moved to Woodville on the Memphis and Charleston Railroad and went into winter quarters.

On the 25^th of February, 1864, the men were mustered in as veterans, and were granted furloughs. They reached Des Moines on the 9th of March, while the Legislature was in session, which adjourned to give the veterans a royal reception. The ladies of the city joined with the General Assembly in tendering to the gallant soldiers a banquet, where all honors were accorded to the boys in blue, who had won fame on so many battlefields. By the first of May, the regiment had again joined the army of General Sherman, which was sweeping onward toward the sea, overcoming all opposition. In the long marches, skirmish lines, and battlefields, Williamson‘s Brigade, composed of the Fourth, Ninth, Twenty-fifth, Thirtieth and Thirty-first regiments, bore a prominent part. In the battle of July 22d, before Atlanta, this brigade made a gallant charge, recapturing De Grass’ famous battery of twenty-four-pound Parrott guns, which had been taken.

A correspondent of the New York Tribune says of Williamson‘s Iowa Brigade, in the battle of the 22d: "It was one of the bravest, truest, most tenacious fighting brigades that has marched to the rescue of our Nation’s liberties." The Fourth had fought bravely at Resaca, New Hope Church, Kenesaw Mountain and at Jonesboro, until losses had reduced its numbers below two hundred. Major Nichols was severely wounded, Captain Anderson was wounded at Jonesboro; Lieutenants Baker and Cramer were killed at Ringgold. Several changes were made in officers; Major Nichols was promoted to lieutenant-colonel, and Captain A. R. Anderson was promoted to major.

In the pursuit of Hood’s army which began October 5th, the Fourth Iowa took part. It remained with Sherman in his march through the Carolinas and fought at Bentonsport, the last battle of that famous campaign. Early in January 1865, Williamson received his well-earned and long-delayed commission as Brigadier-General. The Fourth Regiment marched from Raleigh to Washington and participated in the final grand review, and was then sent to Louisville, where it performed provost duty until mustered out in July 1865. It reached Iowa, at Davenport, on the 28th, numbering four hundred and fifty seven men and twenty-three officers. Entering the service with 1,000 men, three hundred had been added to its ranks as the war progressed. Now, at the close, the 1,300 were reduced by sickness, disability from hard marches, wounds, death, and starvation in Rebel prisons, by nearly eight hundred. Such was the terrible waste of four years of war in one regiment.