April 8, 1864 was the Battle of Mansfield and April 9, the Battle of Pleasant Hill.
Mansfield was a crushing Confederate victory, scattering the Yankees and driving them back down the road in a chaotic retreat. One division of Union forces managed to make a stand on a hill covering the road just as the sun was setting and that saved the Federal army from a total rout. The Yanks retreated 17 miles back to Pleasant Hill during the night, staggering into the town in the morning. One division of Union forces had not been engaged at Mansfield, about 6,000 soldiers, and were well rested. They would be the main Union fighting force later that day.
Meanwhile the Confederates busied themselves ransacking 700 abandoned supply wagons. Confederate cavalry pursued the Yanks to Pleasant Hill and reported that they were digging in for a fight. Fresh troops did arrive, about 4,800 soldiers, who had marched over 25 miles during the day just to reach the battlefield.
At 4PM, April 9, 1864 the largest battle of the "Civil War" fought west of the Mississippi River commenced. At the small town of Pleasant Hill, and in the forests surrounding the town, 12,500 Confederates attacked 12,100 Yankees. The plan went awry for the Confederates when one corps got lost in the thick woods and did not hit the Union line where it had been planned. Still, they were successful destroying an entire Yankee brigade and entering the town...but then those fresh 6,000 Union troops suddenly appeared on their flank. The fighting was close and vicious. By the end of the day...which did not end until 10PM that night with rare night-fighting occurring, the two armies pulled back to their original lines. Each side lost about 1,600 men killed and wounded. The next day the Union army began its retreat 40 miles back to Natchitoches.