President Andrew Johnson succeeded to the presidency suddenly, when Abraham Lincoln was killed by an assassin. Confronted with the prospect of Reconstruction—bringing the Union back together after a prolonged Civil War—Johnson tolerated harsh treatment of former slaves in Southern states, believing that it was up to the states to determine their status. Johnson clashed with the Republican-led Congress, which favored complete equality for African Americans as part of Reconstruction. He became the first president ever impeached by the House of Representatives, primarily for defying the Tenure of Office Act in seeking to circumvent Congress’s Reconstruction Acts. Johnson barely escaped conviction in the Senate and continued to criticize Congress’s Reconstruction plan until he left office.