After a brief detour to Minnesota during the Sioux Indian Uprising, the 27th reported to Brigadier General William T. Sherman at Memphis, Tennessee, in December 1862.  On New Year's Day, 1863, William and his brothers found themselves on a cold and muddy march from Jackson, Tennessee, to Clinton, on the Tennessee River, in futile pursuit of Brigadier General Nathan Bedford Forest.  Following this march, brother Edward was discharged with tuberculosis.  He died the following year.

Ashline's comrades saw little action through the early months of 1863, finding themselves on garrison duty, guarding trains and supply bases.  One July evening, younger brother George was shot in the leg by a careless private in another company.  By November, George was home in Iowa with a minie bullet lodged in the cartilage of his right knee.  It would remain there until he died in 1927.

In September 1863, William took part in the capture of Little Rock as a participant in Major General Frederick Steele's Arkansas Expedition.  The following March the 27th Iowa was with the XVI Army Corps on Major General Nathaniel P. Banks' Red River Campaign.  At the Battle of Pleasant Hill, Louisiana, William's regiment stood with the 2d Brigade, 3d Division, halted the Confederate onslaught directed by Lieutenant General Richard Taylor, and covered Banks' retreat to Grand Ecore.

In early December the 27th Iowa moved to Nashville, Tennessee, with the XVI Corps under Major General A. J. Smith.  Here, on December 16, 1864, Ashline and his regiment, in the left flank brigade under command of Colonel J. I. Gilbert, struck the center of Lieutenant General John B. Hood's line between Shy's Hill and Overton Hill, overrunning the Confederate entrenchments and witnessing the destruction of the small, but once-mighty Army of Tennessee.

As the war drew to a close, Ashline saw action in the Mobile Campaign, fighting in one of the last major land battles of the conflict at Fort Blakely, Alabama.  Afterward, the 27th Iowa became part of the occupation forces in Montgomery, Alabama.  In June 1865, brother Hiram went home with an unnamed disability.  Soon after, the regiment transferred to Vicksburg, Mississippi, and then home, mustering out at Clinton, Iowa, on August 8.

Ashline died in 1919 at Edgewood, Iowa.  But years before, the clerk of Company E. one Crable, saw fit to list the battles in which William Ashline had taken part, entering them in his permanent service record.  The final words read:  "Character good."