On Monday morning, July 28, 1862, pursued by more than 700 mounted Union troops under Col. Odon Guitar, about 260 Confederate horsemen under Col. Joseph C. Porter entered the vicinity of Moore's Mill, now Calwood. About two miles north, near Old Auxvasse Presbyterian Church, Guitar divided his command, sending nearly two-thirds of his force under Lt. Col. William Shaffer across and south down Auxvasse Creek while the rest, including elements of the 9th Missouri State Militia Cavalry, three companies of the 3rd Iowa Cavalry under Maj. Henry C. Caldwell and Capt. George Duffield, and a section of the 3rd Indiana Battery, continued in pursuit. Porter left a clear trail across an oat field to lure Guitar into an ambush near a deep ravine east of the Moore's Mill-Galbreath Mill road and about one mile south of the Fulton-St. Charles road. Around 11 a.m. to noon, Porter's men moved from a sheltered camp in the ravine to thick brush beside the road, where they ambushed Duffield's advance guard of 25 men. Guitar ordered the advance to dismount, then brought up his main column to deploy on both sides of the road under heavy fire. By about 12:10 p.m., Caldwell's remaining troops and the artillery reached the field, and Guitar had a cannon brought forward by hand because the road was so narrow. Capt. Alvin Cobb's men crossed the road to attack Guitar's right flank, and Guitar answered by deploying a second cannon and pushing his right flank forward. Between about 12:30 and 12:45 p.m., Porter ordered a furious charge with a Rebel Yell that drove the Federals from their cannon and back to the rear, killing four cannoneers and several nearby troops, including a bugler. Guitar finally rallied his men about 100 yards back, and from 12:45 to 1 p.m. both sides launched repeated charges and countercharges without gaining an advantage. From 1 to 1:30 p.m., Shaffer's absent force finally reached the battlefield, including detachments of Merrill's Horse Battalion, Companies B and D of the 10th Missouri State Militia Cavalry, and 38 Louisiana Independent Red Rovers cavalrymen. After stripping excess gear, they entered the fight dismounted, with one company held in reserve, another sent to reinforce the right flank, and the rest extending the extreme left past Porter's right. Porter answered by withdrawing his line 50 to 75 yards, still 25 to 50 yards ahead of its original position. From 1:30 to 3:30 p.m., constant pressure and superior Federal numbers slowly turned the fight as their extending flanks began to enclose Porter's force. By 2:30 or 3 p.m., Porter's men were conserving dwindling ammunition, while the recaptured Federal cannon on the right flank poured canister into Cobb's men. Between 3:30 and 3:45 p.m., Porter ordered an orderly withdrawal to the ravine camp, but the companies of Capt. Sylvester Penny and James W. Porter, the colonel's brother, did not receive the word and remained in place. Between 3:45 and 4 p.m., they finally withdrew under intense fire from the encircling Federals. As Penny and three others tried to carry off a wounded man who asked to be left behind, a round of canister from the forward cannon killed several of them, including Penny. The remaining Confederate troops left the field to the Federals, who were too exhausted to pursue.
