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Battles

The first battle of the Trans-Mississippi theater was the Battle of Wilson's Creek (August 1861). The Confederates were driven from Missouri early in the war as a result of the Battle of Pea Ridge.

Extensive guerrilla warfare characterized the trans-Mississippi region, as the Confederacy lacked the troops and logistics to support regular armies that could challenge Union control. Roving Confederate bands such as Quantrill's Raiders terrorized the countryside, striking military installations and civilian settlements. The "Sons of Liberty" and "Order of the American Knights" attacked pro-Union people, elected officeholders, and unarmed uniformed soldiers. These partisans could not be driven out of Missouri, until an entire regular Union infantry division was engaged. By 1864, these violent activities harmed the nationwide antiwar movement organizing against the re-election of Lincoln. Missouri not only stayed in the Union, but Lincoln took 70 percent of the vote to win re-election.

Small-scale military actions south and west of Missouri sought to control Indian Territory and New Mexico Territory for the Union. The Battle of Glorieta Pass was the decisive battle of the New Mexico Campaign. The Union repulsed Confederate incursions into New Mexico in 1862, and the exiled Arizona government withdrew into Texas. In the Indian Territory, civil war broke out within tribes. About 12,000 Indian warriors fought for the Confederacy but fewer for the Union. The most prominent Cherokee was Brigadier General Stand Watie, the last Confederate general to surrender.

After the fall of Vicksburg in July 1863, Jefferson Davis informed General Kirby Smith in Texas that he could expect no further help from east of the Mississippi. Although he lacked resources to beat Union armies, he built up a formidable arsenal at Tyler, along with his own Kirby Smithdom economy, a virtual "independent fiefdom" in Texas, including railroad construction and international smuggling. The Union, in turn, did not directly engage him. Its 1864 Red River Campaign to take Shreveport, Louisiana, failed and Texas remained in Confederate hands throughout the war.