Acting Assistant Surgeon Henry Rinaldo Porter was the sole surviving surgeon with Custer's 7th Cavalry at the Battle of the Little Bighorn. Surgeon James DeWolf was killed in the retreat from the valley floor and Surgeon George Lord had gone off with Custer (to perish with him). For much of two days Doctor Porter was the only trained medical professional caring for what eventually grew to be 30 wounded men. His improvised field hospital at the Reno-Benteen defense site was under constant fire from Sioux and Cheyenne riflemen. Though the horses provided some cover, their constant thrashing about from being hit by rifle fire posed a threat to the wounded men lying on the ground. The lack of water for drinking and dressing wounds, however, became the greatest deficiency. Twice during the siege soldier volunteers made runs down to the river for water. It is to Dr. Porter's credit that the great majority of the wounded that came under his care survived.
Porter had laudanum to ease the pain, also morphine sulfate. After removing as much debris as possible, he would use a carbolic-acid solution to sterilize wounds. Projectiles that passed through the body, such as legs, arms and shoulders were more easily cared for. Projectiles that entered large body cavities were inoperable and generally fatal. During the siege, Porter performed two amputations. One was the lower leg of one of the water carriers, Private Mike Madden. The other was the upper half of the middle finger of Private John Phillips.
Before the Great Sioux War of 1876, Dr. Porter served General Crook in his Apache campaigns in Arizona, from September 22, 1872, to April 25, 1873. Crook cited Porter for "conspicuous gallantry in the closing campaign against the Tonto Apaches in February and March, 1873." Porter was a doctor or surgeon for hire under contract for specific periods of time with the army. He was not a soldier. On May 14, 1876, he entered into a three month contract for the Sioux campaign. Porter was 28 years old at the time of the Battle of the Little Bighorn. Before marching into battle, Custer came to Porter and asked him if he would go with his battalion as he was in better health than Dr. Lord, but when Dr. Lord was approached, he only said he would go with the headquarters battalion. This proved to save Porter's life. His contract was cancelled on September 30, 1876, at Fort Abraham Lincoln, and he returned to medical practice in Bismarck, Dakota Territory.
Porter was called to testify at the Reno Court of Inquiry in January 1879. Porter who had been with Reno's battalion, stated that Reno seemed uncertain whether to stay or flee the woods. That the retreat was done with considerable confusion and disorder, he himself being left by the soldiers, and that he was fortunate to secure his horse and ride to safety. He also stated that Captain Benteen was the real commander of the hilltop defense. Of the 23 witnesses who gave testimony, 14 were officers of the 7th Cavalry. The testimony of the five civilians who were at the battle was decidedly more critical of Reno's conduct, than that of the 7th Cavalry officers.
After the Battle of the Little Bighorn, Porter had his accounts of the battle published in the New York Herald, July 11, 1876, as "The Terrible Sioux: Doctor Porter's Account of the Battle" and the Bismarck Tribune, May 24, 1878 as "The Brave Doctor." He died at the age of 54 on March 3, 1903, in the Hotel Metropole, Agra, India.