The trenches at Petersburg ran for 37 miles.

I've stood where they used to be — outside the city now called Petersburg, Virginia, in a national park where the earthworks have been preserved under mowed grass. They look small. They don't look like the place where the Civil War was decided over the course of 292 days.

How It Started

By June 1864, Ulysses Grant had been hammering at Lee's Army of Northern Virginia for six weeks in some of the most sustained and brutal fighting the war had produced — the Wilderness, Spotsylvania, Cold Harbor. Lee had held, but only by retreating southward, trading space for survival. The Confederate army was smaller after each engagement. The Union could replace its losses. The Confederacy could not.

Petersburg was the key. The city, 25 miles south of Richmond, was the junction point for five railroads that fed both the Confederate capital and Lee's army. Take Petersburg, and Richmond fell. Lee understood this. He had told his commanders that if Grant ever got to the James River, it was only a question of time.

Grant got to the James River.

The Union Army moved with unusual speed and crossed the James on a 2,100-foot pontoon bridge in mid-June 1864 — one of the great engineering feats of the war. For a critical 48 hours, Petersburg was defended by a skeleton force under the capable but outnumbered P.G.T. Beauregard. Union commanders, cautious after Cold Harbor's bloodbath, attacked timidly and were repulsed. Lee arrived with the main army on June 18.

The siege began.

Life in the Trenches

The trenches at Petersburg were not the mud-floored, rat-infested horrors of World War I, but they were no less miserable. Sharpshooters made moving above the parapet fatal. Artillery fire came without warning. The summer heat was brutal; the winter that followed was worse. Soldiers burrowed deeper and built wooden shelters inside the earthworks. They played cards, wrote letters, drilled when safe to do so, and watched the war drag on.

Both sides extended their lines southward and westward as Grant repeatedly tried to stretch Lee's diminishing army past the breaking point. The Confederate perimeter grew thinner. Supply lines were cut one by one. By early 1865, Lee's soldiers were receiving reduced rations — then no rations.

Disease, desertion, and attrition did what Union bayonets had not managed. Between June 1864 and April 1865, the Confederate Army of Northern Virginia lost roughly 28,000 men to desertion alone.

The Mine

The most dramatic moment of the siege came on July 30, 1864, when Union engineers detonated 8,000 pounds of black powder under a Confederate salient, blowing a crater 170 feet long and 30 feet deep into the Confederate line. The explosion worked perfectly. What followed it did not — Union troops poured into the crater rather than around it and were slaughtered by Confederate counterattacks. The Battle of the Crater became a Union catastrophe, with 3,798 casualties. It changed nothing about the siege's mathematics.

The End

By late March 1865, Lee's army — fewer than 60,000 effective troops against Grant's 124,000 — was at its absolute limit. On April 1, Phil Sheridan's cavalry and infantry smashed the Confederate right at Five Forks, cutting the last railroad. Lee informed Jefferson Davis that Richmond must be evacuated.

On April 2, Lee's lines broke. The Confederate army fled west. Grant occupied Petersburg and Richmond on April 3. Within a week, Lee surrendered at Appomattox.

The siege had been a grinding, attritional mathematical problem, and Grant had solved it the only way it could be solved: by making Confederate losses impossible to replace, by cutting supply lines one at a time, and by waiting for arithmetic to do what assaults could not. It was not glorious. It was effective.

The 37 miles of trenches are still there. Some of the earthworks are still five feet high.