The Siege of Petersburg (June 1864 to April 1865), or the Richmond-Petersburg Campaign, was among the last military operations of the American Civil War (1861 to 1865). It was not a siege in the traditional sense, but rather a period of static trench warfare. Both the Union and Confederate armies spent months in their opposing trenches around the vital railway junction of Petersburg, Virginia, wearing one another down through battles, raids, and attrition. By April 1865, the Confederate army buckled under the pressure and retreated, abandoning both Petersburg and the capital, Richmond, to the Union. Shortly thereafter, Confederate Gen. Robert E. Lee surrendered at Appomattox Court House, effectively ending the war.

By early June 1864, the eastern theater of the American Civil War reached a stalemate. Over the past 40 days, the Union Army of the Potomac and the Confederate Army of Northern Virginia had been locked in a life-or-death struggle that had played out over the course of three almighty battles: the Battle of the Wilderness (5 to 6 May), Battle of Spotsylvania Court House (8 to 21 May) and Battle of Cold Harbor (31 May-12 June). Now, with over 80,000 men killed, wounded, or captured between them, the exhausted armies rested within their entrenchments at the crossroads of Cold Harbor in Central Virginia, each side anxiously waiting for the other to make a move.

Lt. Gen. Ulysses S. Grant, general-in-chief of all Union armies, meant to break the deadlock and sidle around the rebel army. He had previously declared that he would fight it out along this line even if it "takes all summer" (quoted in McPherson, 731). True to his word, Grant meant to cross the James River and strike at Petersburg, a vital railway junction 24 miles (39 km) south of the Confederate capital of Richmond.

By capturing Petersburg, he would be effectively isolating Richmond, leaving his opponent, Gen. Robert E. Lee, with two choices: abandon the defense of Richmond or fight it out on open ground of Grant's choosing. So, on 12 June, Grant instructed Maj. Gen. George Gordon Meade – the formal commander of the Army of the Potomac, despite Grant's superseding authority – to be ready to march that night, hoping to cross the James without drawing Lee's attention.

On the night of 12 June, the Army of the Potomac quietly stole away from Cold Harbor. By the next morning, one Union corps was already moving toward the James by water, while the other four travelled overland, making repeated feints toward Richmond to confuse the enemy as to their intentions. The ploy worked – for once, Lee was unable to divine Grant's intentions. The Confederate general decided to keep his army where it was, lest he wind up marching it in the wrong direction.

On 14 June, the Union soldiers began to cross the James, marching over a 2,100-foot-long (640 m) pontoon bridge – the longest in military history – that had been painstakingly constructed by Grant's engineers. The next day, the XVIII Corps under Maj. Gen. William 'Baldy' Smith became the first element of the army to approach Petersburg. Smith was dismayed, however, to find that the city was not undefended. Rather, a token garrison of 2,500 Confederates awaited him, fortified behind a 10-mile (16 km) arc of twenty-foot-thick (6 m) trenches and 55 artillery batteries known as the Dimmock Line.

These rebel defenders, under Gen. P. G. T. Beauregard, were not the cream of the Confederate crop. Indeed, most of them were old men or young boys who Beauregard had hastily scraped together, pressing rifles into their hands for the defense of Petersburg. The Dimmock Line, on the other hand, was no joke. Named for Confederate engineer Captain Charles Dimmock, the line had been continually under construction since early 1862, strengthened and elongated by hundreds of slaves. Now, it was a formidable line of fortifications that Smith knew he could not assault without risking heavy casualties.

Still, he had to try and force a breakthrough before the inevitable arrival of Lee's army. So, on the evening of 15 June, he launched his assault, his blue-coated troops rushing toward the Dimmock Line. The Union attack was partially successful; before sunset, the Yankees had captured over a mile of line and sixteen cannons. As the pale moonlight shone through an ink black sky, Buearegard pulled his survivors back to a new line, his desperation apparent in the message he sent to Lee: "Unless reinforcements are sent before forty-eight hours, God Almighty alone can save Petersburg and Richmond" (quoted in Foote, 439).

At dawn on 16 June, Smith was joined by the Union II Corps under Maj. Gen. Winfield Scott Hancock. That day, Smith and Hancock launched another assault that captured more of the rebel lines but did not achieve a breakthrough. By the next day, Lee realized that the force facing Beauregard at Petersburg was no mere demonstration – rather, Grant was bringing his whole army to bear on the city. Utilizing his customary speed, Lee rushed over the entire Army of Northern Virginia to bolster the Petersburg defenses (except for the Second Corps, under Jubal Early, which was currently off wreaking havoc in the Shenandoah Valley, in the direction of Washington).

On the morning of 18 June, Gen. Meade arrived, frustrated to find that the Army of the Potomac had not yet stormed the Petersburg fortifications. "What additional orders to attack you require I cannot imagine," he grumbled to one corps commander, telling another to "attack at all hazards" (quoted in McPherson, 741). The Yankee soldiers went forward in yet another assault, but this time, they encountered not just Beauregard's green recruits, but Lee's hardened veterans. They met with heavy fire and sustained serious casualties. In one Maine regiment, 632 of 850 men were killed or wounded in this single action.

Toward the evening, Meade called off any further assaults. Grant himself had arrived on the scene by then, recognizing that the soldiers were not fighting with the ferocity that they had even a month ago at the Wilderness. This could be explained by both fatigue suffered by the veterans after a month of constant fighting and the fact that a decent portion of the soldiers who had begun the campaign were now rotting in their shallow graves. Realizing that he needed to shift tactics, Grant decided to settle in for a siege. "We will rest the men," he said, "and use the spade for their protection until a new vein has been struck" (ibid).

And so, each army spent the last week of June digging in. The Union army dug its own line of trenches, while the Confederates strengthened their existing lines. One section of the Union line was only 150 yards (137 m) away from a rebel saliant, where the Confederates had built a makeshift fort on high ground. One day in late June, Col. Henry Pleasants of the 48th Pennsylvania – a regiment made up largely of coal miners – was peering out at the rebel bastion when he overheard one of his men say, "We could blow that damned fort out of existence if we could run a mine shaft under it" (quoted in Foote, 531).

Pleasants, a former civil engineer, liked that idea. He took it to his division commander, who, in turn, took it to the commanding general of the Union IX Corps, Ambrose E. Burnside. Although some nay-sayers argued that such a mine was impossible – no tunnel could exceed 400 feet (122 m), they said, because it would be impossible to keep it ventilated with fresh air – Burnside gave his approval, if only to keep his men busy. Pleasants and his miners spent the next month burrowing beneath the earth, working in rotating shifts so that the digging could continue around the clock. For ventilation, they used a coal-mining shaft with a fire at the base, which created a draft and pulled in fresh air through a pipe.

By 17 July, against all odds, Pleasants had built a 511-foot-long (156 m) tunnel that ended just beneath the Confederate fort. Here, at the end of the tunnel, Pleasants' men placed four tons of gunpowder. The plan, approved by Meade and Grant, was to blow up the fort and then rush Burnside's infantry corps into the resultant gap. Burnside designated one division of all-Black troops to lead the assault; these soldiers spent the next few days undergoing specialized training, eager to "show the white troops what the colored division could do" (quoted in McPherson, 759).

But at the last minute, Meade changed the plan. For political reasons, he and Grant did not want to send an all-Black division in first – if the assault went awry, they worried they would be accused of "shoving these people ahead to get killed because we did not care anything about them" (ibid). So, they ordered an all-White division to lead the assault instead, even though these soldiers had not been trained for the attack. On 28 July, Grant ordered Hancock's II Corps to create a diversion on the far side of the James, thereby siphoning some of Lee's troops away from the center. This was accomplished, and, at 4:44 a.m. on 30 July, the fuse was set, and the powder exploded.

One eyewitness described the resulting eruption:

A slight tremor of the earth for a second, then the rocking as of an earthquake and, with a tremendous blast which rent the sleeping hills beyond, a vast column of earth and smoke shoots upward to a great height, its dark sides flashing out sparks of fire, hangs in the air for a moment and then, hurtling down with a roaring sound, showers of stones, broken timbers, and blackened human limbs, subsides – the gloomy pall of darkening smoke flushing to an angry crimson as it floats away to meet the morning sun.

(quoted in Foote, 535)

The explosion immediately killed 250 to 350 Confederate soldiers and made a crater 170 feet (52 m) long, 60 feet (18 m) wide, and 30 feet (9 m) deep – this crater is still visible today. An all-White Union division, under Brig. Gen. James Ledlie, charged forward, toward the gap. Not only had these soldiers had no training, but they had been chosen by a drawing of straws, while their commanding officer, Ledlie, reportedly stayed behind in the trenches getting drunk on rum stolen from the surgeon. Thus, these ill-prepared and leaderless soldiers ran directly into the crater instead of fanning out left and right to attack the rebel flanks.

It was not long before the Union soldiers found themselves trapped in the crater, their discipline quickly devolving into panic as they packed in so tightly that they could not move. The Confederates gathered on the edge of the crater, firing into the writhing mass of Union soldiers below with rifles and artillery. In the confusion, more of the Union soldiers were sent into the crater where they became fresh fodder for the rebel guns.

These included the Black troops, the sight of whom enraged the Confederates; when some of these Black soldiers tried to surrender, they were shot dead by the Southerners. When all was said and done, the Union suffered 4,000 casualties for little gain, against less than 1,000 Confederate losses. Ledlie and indeed Burnside were ousted from command for this botched assault, which Grant referred to as "the saddest affair I have witnessed in the war" (quoted in McPherson, 760).

Despite the disastrous results of the Battle of the Crater, Grant did not stop looking for ways to pull the rug from underneath Lee's army. In August, he sought to threaten the rebel supply lines along the Weldon Railroad. On 18 August, the Union V Corps under Maj. Gen. Gouverneur K. Warren reached the railroad at Globe Tavern, where it clashed with the Confederate Third Corps under Lt. Gen. A. P. Hill; Warren was forced to withdraw after suffering 4,500 casualties, compared to only 1,600 rebel losses.

On 23 August, Hancock's II Corps struck the railroad at Reams Station. The II Corps, once considered the best in the army, was not what it used to be – most of the hardened veterans were either dead or home after their enlistments expired, and the recruits who had replaced them were not up to the task. The II Corps was repulsed after losing 2,700 men and a dozen battle flags. Having never before tasted such a bitter defeat, Hancock would soon leave the army in disgust, citing his old Gettysburg wound as an excuse.

Such sorties as these were becoming increasingly uncommon, however, as the campaign took up the characteristics of static trench warfare. Each army brought up mortars, which were used to lob huge shells onto the heads of the helpless soldiers in the opposite trenches. Sharpshooters, too, were a daily threat, taking shots at men who happened to raise their heads a little too far out of their entrenchments. On one occasion, a captain and a private in the 17th Georgia were both killed by the same bullet, after accidentally exposing their heads while passing one another in the trench.

Disease, too, became endemic, especially as winter came on. Smallpox, scurvy, and measles afflicted men on both sides, although the malnourished Confederate soldiers were hit hardest. The rebels lacked enough rations, and what meat they did have was often spoiled; indeed, one Confederate soldier would recall their rations of bacon being "a peculiarly scaly color…full of rancid odor and utterly devoid of grease…it could not be eaten raw and imparted a stinking smell when boiled" (quoted in Foote, 629). This situation was temporarily relieved in mid-September, when Wade Hampton led 4,000 rebel cavalrymen in a raid that captured 2,000 cattle. The Confederates feasted on beef for the next month until the supply was exhausted.

As the New Year approached, the armies remained in their trenches, each side constantly expanding or contracting its line to counter moves made by the other. By now, Lee had stretched his army dangerously thin. His 55,000 troops were responsible for a line of entrenchments that stretched for over 30 miles (48 km) from Petersburg to the eastern outskirts of Richmond. Lee was aware that he could not keep this up forever – desertion, attrition, and battlefield deaths were rapidly whittling his army down, and reinforcements were not coming in fast enough to replace these losses.

In February 1865, Lee was appointed general-in-chief of all Confederate armies. This came at a time when the Confederacy was being suffocated from all sides; the Confederate Army of Tennessee had been obliterated at the Battle of Nashville, while Union Maj. Gen. William Tecumseh Sherman was rapidly advancing northward through the Carolinas. Lee knew that the time had come for him to break out of Petersburg, lest he find himself encircled by Grant on one side and Sherman on the other. Leaving Petersburg would mean abandoning the city – and by extension, Richmond – to the enemy, but Lee believed it more important to preserve his army to fight another day.

On the night of 24 March, he made his move, launching an assault on the eastern end of the Union line at Fort Stedman. Initially, the attack was successful; the rebel troops swarmed into Fort Stedman and captured half a mile of Union trenches. However, their assault soon lost momentum, and the Union recovered the lost territory in a spirited counterattack. Lee had paid dearly for this gambit, losing 5,000 men while failing to break out of Grant's tightening noose.

On 29 March, Grant retaliated by ordering troops under Maj. Gen. Philip H. Sheridan to strike the right flank of the Confederate line. Lee hurried over two divisions under Maj. Gen. George E. Pickett to bolster the flank, leading to the Battle of Five Forks on 1 April. After a day of desperate fighting in the driving rain, Pickett's divisions collapsed, half of the men surrendering and the other half running off in panic. When Grant learned of the victory at Five Forks, he took it as a sign that the rebel line was close to breaking and ordered an assault all along the line to take place the next morning.

On 2 April, the Union soldiers charged forward, breaking through the rebel line at several places. Though the Confederates fought valiantly, they had been significantly weakened by the last nine months of siege and were swept back. They suffered heavy losses – including A. P. Hill, who was killed – and were forced back into their inner line of defenses. Lee saw the writing on the wall. That night, he gathered his survivors and marched out of Petersburg, beating a hasty retreat into the countryside.

On the morning of 3 April 1865, the Union Army of the Potomac occupied Petersburg, its prize after the long and grueling siege. There was now nothing standing between Grant and Richmond, which fell that same day; Confederate President Jefferson Davis and his government had evacuated the city mere hours before. Having devoured the heart of the Confederacy, Grant then took off after Lee, catching up with him outside Appomattox Court House. Following a brief battle, Lee surrendered to Grant on 9 April 1865, effectively bringing the Civil War to an end.

The Siege of Petersburg, then, was a significant military operation that directly led to the weakening of Lee's army, the capture of Richmond, and the end of the war. It had been costly – during the course of the almost ten-month siege, the Union had suffered roughly 42,000 casualties while the Confederates had lost about 28,000. The siege bore another significance, one that would not be recognized for another half century. The static trench warfare of Petersburg would be repeated on a much larger scale on the fields of Western Europe in the First World War (1914 to 1918).