Tennessee's strategic location made it a prime target of the Union armies during the Civil War. It was, in fact, the only Confederate state that came entirely under Union control before the war ended.
The invasion of Tennessee began early in 1862 when Federal land and naval forces under Ulysses S. Grant moved against Fort Henry on the Tennessee River and Fort Donelson on the Cumberland River, both of which fell in February. Grant's forces proceeded to penetrate deep into the state along the Tennessee; meanwhile, another Federal army under Don Carlos Buell captured Nashville (February 25) and Confederate forces abandoned Middle Tennessee. The governor, legislators, and other state officials fled from Nashville to Memphis, which was itself captured on June 6, 1862, by Union forces advancing down the Mississippi River. The Confederate state government thereupon ceased to exist.
West Tennessee remained in Federal hands for the rest of the war. Confederate forces reoccupied the southern part of Middle Tennessee in the fall of 1862, but were again expelled from the region in July 1863 by Buell's successor, William S. Rosecrans. After that, except for the Confederate Army of Tennessee's briefly occupying the southern counties in November-December 1864, Middle Tennessee remained under Union control.
East Tennessee eluded the Federals' grasp considerably longer than the other two regions. Not until late August 1863 did a Union army enter the region, advancing southward from Kentucky. That army, under the command of Ambrose Burnside, captured Knoxville on September 1. Rosecrans moved eastward and seized Chattanooga that same month. Grant then succeeded Rosecrans, and in late November 1863 he drove the Confederate Army of Tennessee into Georgia. At the same time, Burnside repulsed a Confederate force sent to recapture Knoxville. That force then withdrew into upper East Tennessee; when it moved on to Virginia in the spring of 1864, Tennessee was wholly in Federal hands.
As Union commanders seized Tennessee piece by piece, they imposed martial law and posted garrison forces in the important towns, including Clarksville, Murfreesboro, Columbia, Jackson, Knoxville, Chattanooga, Memphis, and Nashville. These last three, especially Nashville, became major Union military centers, occupied by thousands of Federal troops and support personnel and crowded with supply depots and hospitals.
Throughout most of 1862, Federal authorities pursued a lenient occupation policy in the hope of winning over secessionist citizens, who comprised the great majority of citizens in Middle and West Tennessee. But finding that the secessionists remained hostile and defiant, the authorities adopted an increasingly harsh policy. This included the seizure and destruction of private property, the imprisonment or banishment of those who refused to take an oath of allegiance to the Union, and the forcible emancipation of slaves. (Though Tennessee was exempted from President Abraham Lincoln's Emancipation Proclamation of January 1, 1863, military authorities generally ignored that exemption when dealing with secessionist slave owners.)
Military rule over the civilian populace was complicated by a conflict of authority between the Union army commanders and Military Governor Andrew Johnson, who was appointed by President Lincoln and sent to Nashville in March 1862 with orders to reconstruct the state government. Arguments with the generals exasperated Johnson, but even more frustrating to him was the continuing defiance of Middle and West Tennessee secessionists, who would have nothing to do with Reconstruction. Nor did the capture of East Tennessee, with its predominantly Unionist population, bring the speedy revival of state government that Johnson sought, as his increasingly radical stance on such issues as emancipation provoked opposition from conservative Unionists. Not until April 1865 was civil government restored in Tennessee, under a new state constitution written by radical Unionists and endorsed by Johnson.
For most Tennesseans, Union occupation was a devastating experience. Many secessionist citizens, appalled by the prospect, fled at the approach of the Yankees and lived as refugees in the Deep South for the duration of the war. Those who stayed faced the agonizing decision of whether, and to what extent, to resist the enemy. The great majority did resist to some degree; the boldest went beyond defiant words and noncooperation to engage in active resistance: smuggling, spying, and even guerrilla warfare. But in doing so they risked retaliation.
Those who lived in the garrisoned towns found themselves directly under the enemy's thumb and subject to constant scrutiny. But there were compensating advantages. Army authorities, anxious to preserve order around their military posts, provided police and fire protection, health services, and courts of law. They doled out free provisions to the needy and permitted the operation of schools, churches, and markets. People in the garrisoned towns, therefore, could live a relatively normal life despite the war that raged all around them.
In the countryside, by contrast, there was famine, anarchy, and violence. Federal foraging squads stripped the farms of crops and livestock. Local government collapsed, law enforcement evaporated, and in that vacuum of authority appeared bandit gangs that preyed ruthlessly on inhabitants. Traveling about became so dangerous that most rural people simply stayed at home. Schoolhouses and church buildings stood empty.
Amid the chaos and ruin, however, there were signs of joy, not only among the Unionists, who welcomed the Federal troops as saviors, but also among the slaves, who seized the opportunity of invasion to liberate themselves. Even in the early months of occupation, when the Union army's official policy was to avoid interfering with slavery, many slaves ran off to the army camps. As Federal policy turned emancipationist, the trickle of runaways became a flood. Many of those blacks who left their masters made their way to “contraband camps” established by the Union army. There they received food, clothing, shelter, medical care, schooling, and jobs; thousands of the younger black men enlisted in the Union army. Even those blacks who chose not to desert their owners declined in many instances to act any longer as slaves; they refused to obey orders and demanded wages for their labor. Slave owners, having always persuaded themselves that their slaves were docile and contented, were dumbfounded when the truth was revealed.
The collapse of slavery, the widespread suffering and destruction, and the incontrovertible fact of Union military rule undermined Confederate morale in the Volunteer State. Well before their comrades in most other parts of the South, secessionists in Tennessee resigned themselves to defeat and emancipation and ended their resistance to Federal authority.