Final answer:
Thaddeus Stevens, in his reconstruction speech, discussed the Radical Reconstruction policies and criticized Presidential Reconstruction, particularly highlighting the First Reconstruction Act of March 1867 that Congress adopted against President Andrew Johnson's more lenient policies.
Step-by-step explanation:
In his reconstruction speech, Thaddeus Stevens is describing the policies that Congress adopted to counteract Presidential Reconstruction and the Black Codes, specifically referencing the Radical Reconstruction policies and the First Reconstruction Act of March 1867. This act, considered "the most important legislation of the entire period" by historian Samuel Eliot Morison, laid the foundation for the Reconstruction period after the Civil War. The act decreed that no legal state governments or adequate protection for life and property currently existed in the rebel states, with the exception of Tennessee, thereby mandating a more stringent process for reentry into the Union that included the drafting of new state constitutions guaranteeing black suffrage.
President Andrew Johnson’s opposition to the Fourteenth Amendment and his "swing around the circle" speeches aimed at gaining support for his own milder version of Reconstruction increased tensions with congressional Republicans. This conflict paved the way for the Radical Republican agenda led by figures such as Thaddeus Stevens and Charles Sumner, which culminated in the tough measures incorporated in the Radical Reconstruction acts.