Round Mountain Nov. 19, 1861. The exact location of the battle is unknown. It was also between Confederate forces and Indians not regular Union troops. Here's a summary of what happened:
Internal differences within the Creeks (repeated in smaller scale in the decimated Seminole nation) led the aged Chief Opothleyahola to lead a substantial faction (perhaps 3,500 of which 1,000 were warriors) to seek protection from the Federal Government in Kansas. The Confederates wanted to stop this.
Cooper set out on November 15, 1861, with about 1,400 very green men to either compel submission or “drive him and his party from the country”. He led his men up the Deep Fork of the Canadian River to Chief Opothleyahola’s camp which they found deserted. On the 19th, Cooper learned from prisoners that part of Opothleyahola’s band was at the Red Fork of the Arkansas River, where they were erecting a fort.
Cooper’s men arrived there around 4pm and he ordered a cavalry charge which discovered that the Natives had recently abandoned their camp. The Confederates did find some stragglers beyond the camp and followed them, blundering into the new camp. The Natives fired into the Rebel cavalry and moved large numbers to attack them. This chased the Confederate advance guard back to the main body, but did not end the engagement. Darkness prevented Cooper from attacking until the bulk of the Natives were within 60 yards. A short fight ensued but Opothleyahola’s men broke it off and fell back to their camp.
Cooper did not want his raw troops to try anything in the dark, and waited until the morning of the 20th. Again they found Opothleyahola’s campsite, but the fugitives were gone.
The Confederates claimed victory for pushing Opothleyahola out of the area, but it was only the first of three encounters between Opothleyahola’s Union supporters and Confederate troops.
This set up the next battle. The battle of Chusto-Talasah on Dec. 9, 1861. Here are the details:
After the defeat of Opothleyahola and his Unionist force at Round Mountain, he retreated northeastward in search of safety. He may have been thinking about moving to Kansas and protection of US Army garrisons, or perhaps just moving away from his pursuers.
On December 9, 1861 Opothleyahola and his followers were at Chusto-Talasah, or Caving Banks, on the Horseshoe Bend of Bird Creek when Cooper’s 1,300 Confederates attacked about 2pm. The Natives knew Cooper was coming and had deployed their fighters in a strong position at the Bend. For almost four hours, Cooper repeatedly attacked and attempted to outflank the Natives. Just before dark the attacks succeeded in pushing Opothleyahola east across Bird Creek.
Cooper claimed another victory, camped on the battlefield overnight but did not pursue because he was short of ammunition. Opothleyahola and his followers moved off in search of security elsewhere