I first met Radovan Karadžić in a war crimes courtroom at the International Criminal Tribunal for the Former Yugoslavia (ICTY). He was there to defend himself against a litany of accusations. I had been called by the prosecution to testify as an expert historical witness to provide background and context to wartime events, having assumed that role in a dozen previous cases before the ICTY. In most other trials, I testified for a few hours under questioning by a prosecutor and was then cross-examined for a few more hours by defense attorneys.

This case was different. In choosing to serve as his own defense attorney, Karadžić gained the opportunity to confront personally each witness, in the presence of three judges who would decide his case. Standing at the defense lectern, he cross-examined me with a barrage of barbed and loaded questions. For a total of twenty-four hours, from June 1 to 10, 2010, he and I engaged in a strange kind of dialogue – testy, impassioned, or sometimes surprisingly cordial – about his rise to power and whether he had led Serb nationalists to commit mass atrocities in Bosnia during the war of 1992–95. Despite the contentiousness of our encounters, with each passing day of the trial I gained new insights about him and the movement that he had led in the 1990s.