The ironclad oath was a key device for the removal of ex-Confederates from the political arena during the Reconstruction of the United States in the 1860s. It required every white male to swear they had never borne arms against the Union or supported the Confederacy. Specifically they swore they "never voluntarily borne arms against the United States," had "voluntarily" given "no aid, countenance, counsel or encouragement" to persons in rebellion and had exercised or attempted to exercise the functions of no office under the Confederacy. Men who took the oath were eligible for office and were called Scalawags--an insulting term at the time now generally used by scholars.
Congress originally devised the oath in July 1862 to exclude pro-southern Copperheads from government by requiring it be sworn by all federal employees, lawyers and federally elected officials. Radical Republicans in Congress attempted to apply it to southern voters in the Wade-Davis Bill of 1864, but Lincoln vetoed it and it never went into effect. Andrew Johnson also opposed it; he and Lincoln wanted Southerners to swear an oath that 'in the future they would support the Union.
When the Radical Republicans gained full control of Congress in 1866 they used the backward-looking Ironclad Oath to prevent former Confederates from voting in the South, or serving on juries. In 1867 the US Supreme Court held that the federal ironclad oath for attorneys and the similar Missouri state oath for teachers and religious ministers were unconstitutional because they violated the constitutional prohibitions against bills of attainder and ex post facto laws.
The ironclad oath was fiercely hated by Southern whites because it stripped most of the region's leaders of political power and seemed to violate the principles of republicanism and consent of the governed. It was effectively ended in 1871 and finally repealed in 1884, but left a lasting legacy of hatred and distrust.
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