When most of what remained of the AoT (after the rout at Nashville) left Tupelo in Jan. '65 and made the difficult trek eastwards over approximately 500 miles to Augusta, it was described by observers as more of a disorganized mob, than an army, of demoralized soldiers. After reaching Augusta, the majority of them then headed north to Raleigh, staying west of Sherman's northwards push through SC.
However, when Joe Johnston took over army command in late Feb. and was ordered by Lee to concentrate his scattered forces to drive back Sherman's advance, his return was enthusiastically welcomed by these AoT veterans - morale improved and discipline was restored significantly among them.
By mid-Mar., Johnston had a little more than around 20,000 men in the field and he formed the 'Army of the South' from the four distinct forces now under his immediate command. One of those distinct forces included the remnants of the AoT (of about 6,000 effectives), which constituted a sizeable portion of his assembled small army.
But when re-appointed to this high command role, Johnston knew (and he told Lee such) that his small army was too weak to stop Sherman's vastly superior numbers of toughened veterans rolling forward. 'Old Joe' believed that his only hope throughout this period was to delay Sherman's advance long enough to try and force peace negotiations on more favorable terms.