The main argument for the Freedmen's Bureau, which was more or less unprecedented in the nation's history, was that freed slaves as well as poor whites would need major, if temporary assistance to make their way in the postwar South. In short, it was seen for the most part as providing support for the transition from slavery to freedom. The perceived needs can be seen in the roles the Bureau took up in the early days of Reconstruction. Its initial role was primarily to provide aid and relief to former slaves in the ruined South. As Bureau officials recognized the social realities of the postwar South, they began to negotiate contracts on behalf of freedmen, set up schools, and assisted blacks in registering their marriages, which had of course not been legally recognized under slavery. The version of the Freedmen's Bureau law passed by Congress (and vetoed by President Andrew Johnson) extended the Bureau's mandate to include many of these needs. The law went into effect as Congress voted to override the president's veto in 1866.