What did president johnson do to warrant articles of impeachment being brought against him?

In May, 1868, the Senate came within a single vote of taking the unprecedented step of removing a president from office. Although the impeachment trial of Andrew Johnson was ostensibly about a violation of the Tenure of Office Act, it was about much more than that. Also on trial in 1868 were Johnson's lenient policies towards Reconstruction and his vetoes of the Freedmen's Bureau Act and the Civil Rights Act. The trial was, above all else, a political trial.