In U2 at the End of the World by Bill Flanagan U2 promised to give Sarajevo a concert on the night of July 3, 1993. They weren't able to give it then since it was still a highly dangerous place to throw a concert. That's why they waited until the Popmart tour to finally give them the concert they had promised.
It all started when American aid worker Bill Carter snuck backstage at a concert in Verona, Italy hoping to capture U2 on video offering their support for the civilians of Sarajevo dealing with the sniper war. In a few dates of the European Zoo TV tour in England, Bono allowed Bill Carter, who was fully equipped with a video camera, to get ordinary people of Sarajevo to voice their opinions on the war that beleaguered them during a handful of concerts. The motive that U2 had to broadcast the footage was on account of there not being enough media attention to those suffering in Sarajevo who needed help; especially since practically nothing was being done to provide the people of Sarajevo with food and clothing.
As for "Miss Sarajevo," one of the stories that Carter passed to U2 the same night in Verona was the surreal event that took place during a massive hurricane amidst the war -- a beauty pageant. The incident motivated Bono to push Bill Carter into making an award-winning documentary on the event titled "Miss Sarajevo." And as you know, it also inspired Bono write the song based on the event with the same title.