The formidable weapon in Southern diplomacy during the tenure of Abraham Lincoln was Cotton.
Explanation:
1. Cotton was a key resource in the South during the Civil War due to its economic importance.
2. The South used cotton as a diplomatic tool by limiting its export to European countries that relied on Southern cotton for their textile industries.
3. By controlling the supply of cotton, the South hoped to pressure European nations like Britain and France to support the Confederacy in the war against the Union.
4. This tactic was part of the South's overall diplomatic strategy to gain international recognition and support during the Civil War.
