The Battle of Mansfield, also known as the Battle of Sabine Cross-Roads or Pleasant Grove, on April 9, 1864 in De Soto Parish, Louisiana, was the first major clash of the Union's Red River campaign.

Maj. Gen. Nathaniel P. Banks's Union contingent of over 12,000 men ascended the Red River to within 25 miles of the Texas border, but lost contact with the accompanying gunboat fleet, due to low water conditions and the necessity for the army to follow an established road that turned inland away from the river. Maj. Gen. Richard Tayor, in command of the Confederate forces, along with his subordinates Brig. Gen. Tom Green and Maj. Gen. Camille de Polignac, determined to make a stand near Mansfield against the direct orders of his more cautious superior, Major General E. Kirby Smith, the commander of all Confederate forces west of the Mississippi River.

Green's cavalry harassed the Union vanguard as they advanced. Confederate forces attacked the disorganized Federals and decisively routed them. Both pursuit and reinforcement were hampered by the Union wagon train's blockage of the narrow road, which fell into Confederate hands. Banks, despite displaying great personal bravery in attempting to rally his troops, was revealed once again to be a military incompetent. When darkness and stiffening Union resistance ended pursuit, the Union had suffered over 2300 casulties, the loss of supplies, and was demoralized. The Confederates took about 1500 casulties and were consumed with hope that the entire Union expedition could be destroyed.

On April 9, Taylor launched an ambitious assault against the newly reinforced Federals at Pleasant Hill, and had the upper hand before General Thomas J. Churchill's Arkansas division was flanked on its right and repulsed. The Federals remained demoralized and unconfident in their commander, and continued to retreat to Grand Ecore.

The decisive failure of the Red River campaign was a rare bit of uplifting news for the Confederacy in a bleak year. Despite the loss of resources (including the mercurial and beloved Tom Green), the failrue of this offensive helped to prolong the war by tying down Union resources from other fronts.