Richard Millen enlisted in Company A, Savannah Volunteer Guards on April 1st, 1862. This unit would later become known as the 18th Georgia Heavy Artillery Battalion or 18th Georgia Battalion and would serve the early years of the war along the coastline of Georgia and South Carolina. Before being transferred to Virginia under the command of Major William S. Basinger in May 1864, Richard and the Savannah Volunteer Guards had the distinction of defending Battery Wagner near Charleston Harbor. While in Virginia, the 18th Georgia engaged the Yankees trying defending Richmond and Petersburg. Richard would write his sister during this time, stating: “It has been a long time since we have been together; a cruel war has devastated our once beautiful country, many changes have taken place since then, and many more will likely occur before we meet again; if we ever do meet again on this Earth.  Come what may, I hope and pray that I may be able to say with a sincere heart, “O! God thy will, not mine, be done…. If it is God’s will that I am to be debarred the pleasure of again meeting on Earth, those who are dear to me, I look forward to a glorious union in Heaven, where all will be peace and happiness.”

During the Appomattox Campaign, Richard and the Savannah Volunteer Guards served in Col. Stapleton Crutchfield’s Heavy Artillery Brigade, Gen. George Washington Custis Lee’s Division of Gen. Richard Ewell’s Department of Richmond. Due to the inability of dragging heavy artillery cannons, Crutchfield’s heavy artillerymen were converted to infantry, equipped with rifled muskets. On April 6th, 1865, Richard and the Savannah Volunteer Guards were heavily engaged in a vicious and desperate fight for survival along the banks and ridges south of Little Sailor’s Creek. The 18th Georgia repulsed three separate attacks from the 121st New York Infantry, and they fixed bayonets and counter attacked the New Yorkers twice. The flag of the Savannah Volunteer Guard was planted at the center of the battalion and Richard stood right next to them, defending them bravely. Major William Basinger later wrote, “Sergeant Richard Millen stood on the right of them, Sergeant Simeon Morton on the left of them, fighting like lions.” As many members from the 121st New York were killed and wounded trying to capture the colors of the 18th Georgia by charging their position, Richard continued to defend the position. Ultimately the New Yorkers were able to secure the flag after a long and desperate struggle. Basinger would also recount, “Though fighting to the last, all the rest of the command were killed, wounded, or taken.  Sergeants R. Millen and S. Morton stood to the last before their colors, keeping at bay a party of about fifty men, and were the last to fall.”

Richard was killed in action at Sailors Creek. The losses reported in the Savannah Volunteer Guard were 30 killed, 22 wounded, of the 85 engaged; 61% casualties. Richard was among those who were buried on the field following the engagement. However, his remains would be recovered and re-interred in Laurel Grover Cemetery in Savannah, Georgia, where he rests today.