It was launched through the densely forested gulf coastal plain region between the Red River Valley and central Arkansas towards the end of the war.

The expedition was a Union military operation, fought between approximately 30,000 federal troops under the command of Major-General Nathaniel P. Banks, and Confederate forces under General E. Kirby Smith, whose strength varied from 6,000 to 15,000.

The Battle of Mansfield was a major part of the Union offensive campaign, which ended in defeat for General Banks.

The expedition was primarily the plan of Major General Henry W. Halleck, former General-in-Chief of the Armies of the United States.

[3] Other historians have claimed that the campaign was also motivated by concern regarding the 25,000 French troops in Mexico sent by Napoleon III and under the command of Emperor Maximilian.

Halleck's plan, finalized in January 1864, called for Banks to take 20,000 troops up from New Orleans to Alexandria, including the 47th Pennsylvania Infantry Regiment, the only regiment from the Keystone State to fight in this campaign, on a route up the Bayou Teche (in Louisiana, the term bayou is used to refer to a slow moving river or stream), where they would be met by 15,000 troops sent down from Major-General William T. Sherman's forces in Vicksburg, Mississippi, and under the command of Brigadier-General Andrew J. Smith.

Banks would command this combined force of 35,000, which would be supported in its march up the Red River towards Shreveport by Rear-Admiral David Dixon Porter's fleet of gunboats.

[5] This plan was ready to be set in action in early March 1864, after somewhat belated communication initiated by Banks to inform Sherman and Porter of their roles in Halleck's strategy.

Most of Banks' men, accompanied by a large, poorly trained, cavalry force would march north toward the middle river.

[9] While he waited for Banks to arrive, Smith sent Brigadier-General Joseph A. Mower on a successful mission to capture much of Taylor's cavalry and his outpost upriver from Alexandria at the Battle of Henderson's Hill on March 21.

Two weeks earlier, on March 12, 1864, Lieutenant-General Ulysses S. Grant had been named General-in-Chief of the Armies of the United States, replacing Halleck.

In Grant's message, he told Banks it was "important that Shreveport be taken as soon as possible," because A. J. Smith's command must be returned to Sherman by the middle of April, "even if it leads to the abandonment of the main object of your expedition.

On April 2, Brigadier-General Albert L. Lee's division of Union cavalry collided with 1,500 arriving Confederate Texas cavalrymen.

Approaching Pleasant Hill, the Union army was excessively strung out due both to the existence of only a few camping areas with water and the lack of monitoring of the position of the rear elements.

Taylor had stationed one infantry division (led by Brigadier-General Alfred Mouton) in the woods along the edge of the clearing just north of Honeycutt Hill and east of the road.

While Mouton's assault was repulsed by Landram's infantry, Taylor advanced the rest of his entire line, including Walker's division, against the Union left.

However, Confederate soldiers halted to loot some of the Union wagons, giving Banks' troops needed time to fall back.

During the night, Banks decided to withdraw back to Pleasant Hill because of lack of water and the desire to unite with A. J. Smith's men.

[19] Taylor did not learn of Banks' retreat until dawn the next day; he then ordered an immediate pursuit with Brigadier-General Thomas Green's cavalry.

Though part of the advanced Union right had also collapsed, the forces of Smith and Mower next launched a counterattack and, joined by neighboring regiments, they routed Taylor's men from the vicinity of Pleasant Hill.

[21] Short of water and feed for the horses, not knowing where his supply boats were, and receiving divided opinions from his senior officers, Banks ordered a rapid retreat downriver to Natchitoches and Grand Ecore.

Learning that some of Taylor's 5,000 men had gotten south of him and that the fleet had left for Alexandria, Banks ordered a retreat from Grand Ecore.

The rest of the march to Alexandria was unremarkable, but Porter ran into a delaying ambush at the mouth of Cane River after he tarried to blow up the stuck USS Eastport.

General Banks, on arrival near the Mississippi, was met by Brigadier-General Edward Canby, who had been named Bankss superior in a newly created regional department.

Conversely, it may have extended the length of the war by several months,[citation needed] as it diverted Union efforts from the far more important objective of capturing Mobile, Alabama.

The arguments between the two generals resulted in Taylor's transfer to command of the Department of East Louisiana, Mississippi, and Alabama soon after the campaign ended.