American Civil War 101

An Overview of the War Between the States

Casualties near the Dunker Church, Battle of Antietam

Alexander Gardner / Wikimedia Commons / Public Domain 

Fought from 1861–1865, the American Civil War was the result of decades of sectional tensions between the North and South. Focused on enslavement and states rights, these issues came to a head following the election of Abraham Lincoln in 1860. Over the next several months, 11 southern states seceded and formed the Confederate States of America. During the first two years of the war, Southern troops won numerous victories but saw their fortunes turn after losses at Gettysburg and Vicksburg in 1863. From then on, Northern forces worked to conqueror the South, forcing them to surrender in April 1865.

Civil War: Causes & Secession

Abolitionist John Brown
John Brown.

Library of Congress Prints and Photographs Division / Wikimedia Commons / Public Domain

The roots of the Civil War can be traced to increasing differences between North and South and their growing divergence as the 19th century progressed. Chief among the issues were the expansion of enslavement into the territories, the South's declining political power, states' rights, and the retention of the system of enslavement. Though these issues had existed for decades, they exploded in 1860 following the election of Abraham Lincoln who was against the spread of enslavement. As a result of his election, South Carolina, Alabama, Georgia, Louisiana, and Texas seceded from the Union.

First Shots: Fort Sumter & First Bull Run

General P.G.T. Beauregard
General P.G.T. Beauregard.

Civil War Photos / Wikimedia Commons / Public Domain

On April 12, 1861, the war began when Brig. Gen. P.G.T. Beauregard opened fire on Fort Sumter in Charleston harbor forcing its surrender. In response to the attack, President Lincoln called for 75,000 volunteers to suppress the rebellion. While Northern states responded quickly, Virginia, North Carolina, Tennessee, and Arkansas refused, opting to join the Confederacy instead. In July, Union forces commanded by Brig. Gen. Irvin McDowell began marching south to take the rebel capital of Richmond. On the 21st, they met a Confederate army near Manassas and were defeated.

The War in East, 1862-1863

Portrait of Gen. Robert E. Lee
General Robert E. Lee.

Library of Congress Prints and Photographs Division / Wikimedia Commons / Public Domain

Following the defeat at Bull Run, Maj. Gen. George McClellan was given command of the new Union Army of the Potomac. In early 1862, he shifted south to attack Richmond via the Peninsula. Moving slowly, he was forced to retreat after the Seven Days Battles. This campaign saw the rise of Confederate Gen. Robert E. Lee. After beating a Union army at Manassas, Lee began to move north into Maryland. McClellan was sent to intercept and won a victory at Antietam on the 17th. Unhappy with McClellan's slow pursuit of Lee, Lincoln gave command to Maj. Gen. Ambrose Burnside. In December, Burnside was beaten at Fredericksburg and replaced by Maj. Gen. Joseph Hooker. The following May, Lee engaged and defeated Hooker at Chancellorsville, Virginia.

The War in the West, 1861-1863

Ulysses S. Grant
Lieutenant General Ulysses S. Grant.

Library of Congress Prints and Photographs Division / Wikimedia Commons / Public Domain

In February 1862, forces under Brig. Gen. Ulysses S. Grant captured Forts Henry and Donelson. Two months later he defeated a Confederate army at Shiloh, Tennessee. On April 29, Union naval forces captured New Orleans. To the east, Confederate Gen. Braxton Bragg attempted to invade Kentucky but was repelled at Perryville on October 8. That December he was beaten again at Stones River, Tennessee. Grant now focused his attention on capturing Vicksburg and opening the Mississippi River. After a false start, his troops swept through Mississippi and laid siege to the town on May 18, 1863.

Turning Points: Gettysburg & Vickburg

Siege of Vicksburg Lithograph

Kurz & Allison / Wikimedia Commons / Public Domain 

In June 1863, Lee began to move north towards Pennsylvania with Union troops in pursuit. Following the defeat at Chancellorsville, Lincoln turned to Maj. Gen. George Meade to take over the Army of the Potomac. On July 1, elements of the two armies clashed at Gettysburg, Pennsylvania. After three days of heavy fighting, Lee was defeated and forced to retreat. A day later on July 4, Grant successfully concluded the siege of Vicksburg, opening the Mississippi to shipping and cutting the South in two. Combined these victories were the beginning of the end for the Confederacy.

The War in the West, 1863-1865

Battle of Chattanooga
Battle of Chattanooga.

Kurz & Allison / Wikimedia Commons / Public Domain

In summer 1863, Union troops under Maj. Gen. William Rosecrans advanced into Georgia and were defeated at Chickamauga. Fleeing north, they were besieged at Chattanooga. Grant was ordered to save the situation and did so winning victories at Lookout Mountain and Missionary Ridge. The following spring Grant departed and gave command to Maj. Gen. William Sherman. Moving south, Sherman took Atlanta and then marched to Savannah. After reaching the sea, he moved north pushing Confederate forces until their commander, Gen. Joseph Johnston surrendered at Durham, North Carolina, on April 18, 1865.

The War in the East, 1863-1865

Soldiers in the trenches before battle, Petersburg, Virginia
Union forces at the Battle of Petersburg.

National Archives and Records Administration / Wikimedia Commons / Public Domain

In March 1864, Grant was given command of all Union armies and came east to deal with Lee. Grant's campaign began in May, with the armies clashing at the Wilderness. Despite heavy casualties, Grant pressed south, fighting at Spotsylvania C.H. and Cold Harbor. Unable to get through Lee's army to Richmond, Grant attempted to cut the city off by taking Petersburg. Lee arrived first and a siege began. From April 2–3, 1865, Lee was forced to evacuate the city and retreat west, allowing Grant to take Richmond. On April 9, Lee surrendered to Grant at Appomattox Court House.


Assassination of Abraham Lincoln Lithograph by Currier & Ives

Currier & Ives / Wikimedia Commons / Public Domain 

On April 14, five days after Lee's surrender, President Lincoln was assassinated while attending a play at Ford's Theater in Washington. The assassin, John Wilkes Booth, was killed by Union troops on April 26 while fleeing south. Following the war, three amendments were added to the Constitution which ended the system of enslavement (13th), extended legal protection regardless of race (14th), and ended all racial restrictions on voting (15th).

During the war, Union forces suffered approximately 360,000 killed (140,000 in battle) and 282,000 wounded. Confederate armies lost approximately 258,000 killed (94,000 in battle) and an unknown number of wounded. The total killed in the war exceeds the total deaths from all other U.S. wars combined.

Civil War Battles

Battle of Gettysburg by Thure de Thulstrup

Library of Congress / Wikimedia Commons / Public Domain

The battles of the Civil War were fought across the United States from the East Coast to as far west as New Mexico. Beginning in 1861, these battles made a permanent mark upon the landscape and elevated to prominence small towns that had previously been peaceful villages. As a result, names such as Manassas, Sharpsburg, Gettysburg, and Vicksburg became eternally entwined with images of sacrifice, bloodshed, and heroism. It is estimated that over 10,000 battles of various sizes were fought during the Civil War as Union forces marched toward victory. During the Civil War, over 200,000 Americans were killed in battle as each side fought for their chosen cause.

American People and the Civil War

Major General George H. Thomas
Major General George H. Thomas.

Library of Congress Prints and Photographs Division / Wikimedia Commons / Public Domain

The Civil War was the first conflict that saw the large scale mobilization of the American people. While over 2.2 million served the Union cause, between 1.2 and 1.4 million enlisted in Confederate service. These men were led by officers from a variety of backgrounds ranging from professionally-trained West Pointers to businessmen and political appointees. While many professional officers did leave the U.S. Army to serve the South, the majority remained loyal to the Union. As the war began, the Confederacy benefited from several gifted leaders, while the North endured a string of poor commanders. In time, these men were replaced by skilled men who would lead the Union to victory.

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Hickman, Kennedy. "American Civil War 101." ThoughtCo, Jan. 10, 2021, Hickman, Kennedy. (2021, January 10). American Civil War 101. Retrieved from Hickman, Kennedy. "American Civil War 101." ThoughtCo. (accessed March 22, 2023).