As a Southerner, Lanier carefully weighed his options with both the Union and the Confederacy but the Civil War broke out too quickly. As he wrote:
An afflatus of war was breathed upon us. Like a great wind it drew on, and blew upon men, women, and children. Its sound mingled with the serenity of the church organs... It sighed in the half-breathed world of sweethearts... It thundered splendidly in the impassioned appeal of orators to the people. It whistled through the streets, it stole in the firesides, it clinked glasses in bar-rooms, it lifted the gray airs of our wise men in conventions, it thrilled through the lectures in college halls, it rustled the thumbed book leaves of the schoolrooms.
Lanier became a Confederate soldier but, once the war was over, he somewhat regretted the decision. He rejoiced in the overthrow of slavery but mostly he was disappointed at the cost of the war: "a million of men slain and maimed, a million of widows and orphans created; several billions of money destroyed; several hundred thousand of ignorant schoolboys who could not study on account of the noise made by the shells." He lamented the resulting poverty and ruin of so many people.
On April 26, 1870, Lanier gave a public speech, the "Confederate Memorial Address." It begins:
In the unbroken silence of the dead soldierly forms that lie beneath our feet; in the winding processions of these stately trees; in the large tranquility of this vast and benignant heaven that overspreads us; in the quiet ripple of yonder patient river, flowing down to his death in the sea; in the manifold melodies drawn from these green leaves by wandering airs that go like Troubadours singing in all the lands; in the many-voiced memories that flock into this day, and fill it as swallows fill the summer, — in all these, there is to me so voluble an eloquence to-day that I cannot but shrink from the harsher sounds of my own human voice.
In the after effects of war, Lanier calls for silence, for people to listen to nature and, especially, for tranquility. "We shall bear our load of wrong and injury with the calmness and tranquil dignity that become men and women who would be great in misfortune... To-day we are here for love and not for hate. To-day we are here for harmony and not for discord."