The Regiment was them moved to Tennessee where it participated in the Eastern Tennessee Campaign against General Bedford Forrest and General Joseph Wheeler (who would one day be a Union General during the Spanish American War and command Theodore Roosevelt and the Rough Riders).  During the campaign the Regiment captured 574 prisoners, 652 horses and large amounts of stores and equipment, but never really had success against Forrest.

In November of 1863, the 8th was moved to southern Tennessee and was involved in protecting the army from General Longstreet’s advance after the battle of Chickamauga and, in December, participated in the siege of Knoxville and the pursuit of the retreating rebel army.

In February of 1864, the 8th was sent to join General William Tecumseh Sherman in the invasion of Georgia.  Merrick was at Kenesaw Mountain, where another relative, James Richmond, also was taking part.  The 8th was involved in many reconnaissance patrols and raids, well in advance of the main body of Sherman’s army, under direct command of Judson Kilpatrick ( aka “ Kill cavalry”) .  At Macon, Georgia, the 8th was able to capture and burn three entire trains loaded with supplies before being forced off by superior numbers.  Because the 8th was in advance, it was in constant fighting with Confederate forces, and Merrick, along with the Regiment, was in a continuous state of high emotion and action.

At Clifton, Georgia, the 8th, along with General Stoneman’s infantry, became cut off and surrounded.  Rather than surrender with the infantry and be taken prisoner (news about Andersonville was now spreading throughout the Union Army), Col. Mix ,of the 8th,decided to fight their way out instead.  The troopers used sabers to slash their way out of the trap.  During the fight, Col. Mix was captured when his horse was killed.

For the next eight days the 8th fought a constant running battle as they made their way back to the main army, many on foot.  By the time they reached the safety of the Union lines, the 8th had lost 215 officers and men.  Many of the troopers were exhausted and broken, including Merrick.  He had been involved in 34 battles and engagements, been part of several charges into the enemy, and suffered much physical hardship.  In 1864 alone, he had ridden 2,800 miles through hostile territory.  Unable to continue in such active duty, he was transferred to the Veteran’s Reserve Corps on August 10, 1864, where he served as a farrier until the end of the war, being discharged as a Corporal.