The following is from the book, Encyclopedia of Indian Wars, by Gregory F. Michno.
26 July 1865, Casper, Wyoming: After their winter raids, the Cheyennes and Lakotas who had left Colorado and Kansas for the Powder River country in February joined with the Lakotas who had escaped from the army during a relocation march to form a great force. Together they planned a major attack of about 2,500 warriors against Platte Bridge Station, commanded by Maj. Martin Anderson of the 11th Kansas Cavalry. The garrison consisted of about 120 men of Companies C, I and K of the 11th Kansas Cavalry, detachments of Company G, 11th Ohio Cavalry, and some 3rd U.S. Volunteers under Capt. A. Smith Lybe.
Among the officers at the Platte Bridge post was Lt. Caspar Collins, son of the retired colonel of the 11th Ohio Cavalry. On 26 July, soldiers saw numerous Indians north of the North Platte River; this posed a threat to a wagon train expected soon from the west. When Collins was ordered to take some men out to help guard the train, he fully expected to die. Turning to his friend, he said, "Jim, I know I shall never get back alive. Here is my cap that you have admired so much. Keep it to remember me by." With that, he led out 25 men from Companies I and K.
Collins and his men crossed the long wooden bridge across the river and turned west. Riding along the banks near the bluffs, they were jumped by about 1,000 warriors. The soldiers spun around and tried to cut their way back to the bridge. There were so many Indians on both sides that they shot and hit more of their own warriors than cavalrymen.
Meanwhile, Lt. Henry C. Bretney of the 11th Ohio was crossing the bridge with 40 men to help Collins in case there was trouble. Concealed near the bridge were about 200 Arapahos, but when they jumped out, some well-placed volleys drove them back. The path was open for Collins if he could break through.
Collins's fight was so close that the troopers could almost touch the warriors riding alongside them. Collins was wounded in the hip, but he continued riding until he sw a trooper go down and stopped to help him. As he tried to get the man up on his horse, they were both overwhelmed. Bretney held off the Indians until the retreating troopers galloped back across the bridge.
Four other men died with Collins, and eight more were wounded.
Later that day, Lt. George M. Walker, 11th Kansas Cavalry, led 15 men out to repair a telegraph line the Indians had cut in their raid. Capt. Lybe posted a small force to their rear for support. Walker had barely reached the broken line when Lybe signaled that Indians were coming. The men fell back pell-mell as the Indians closed in. The warriors caught four troopers and speared two of them, killing Pvt. James A. Porter and seriously wounding farrier Joseph Hilty, whose horse carried him to safety. Sgt. Duncan McDougal placed his revolver against the ribs of an Indian riding next to him and fired his last cartridge into him. The howitzer at the station held the Indians long enough for the soldiers to retreat behind its walls.
Six soldiers were killed and nine wounded in the second fight. Indian casualties are difficult to separate from the additional losses they took later in the day. It seems probable that five were killed and ten wounded.