What countermeasure did President Abraham Lincoln's administration use during the Civil War?

The decision to suspend the writ of habeas corpus during President Abraham Lincoln's administration was a significant countermeasure taken during the Civil War. This constitutional right protects individuals from arbitrary arrest and detention without just cause. By suspending it, Lincoln aimed to address the pressing need for maintaining public order and security in the face of the rebellion and insurrection that threatened the Union.

Lincoln believed that swift action was necessary to apprehend those deemed to be threats to the nation, including suspected Confederate sympathizers and those believed to engage in activities that could undermine the war effort. This decision, while controversial, was seen as a measure to prevent dissent and maintain the stability of the government during a tumultuous time. The suspension allowed for military authorities to detain individuals without formal charges, thereby enabling the Union to respond more effectively to security threats.

In this context, the other options, while related to actions taken during the Civil War, do not capture the same level of constitutional impact or significance as the suspension of habeas corpus. The declaration of martial law and the creation of the Secret Service, for example, were important, but the suspension of habeas corpus directly addressed the balance between civil liberties and national security, making it a pivotal action during Lincoln's presidency.