Okay, I'll try. In SOTE Luke leads a squad of Bothan piloted Y-Wings against the freighter that held the plans to the DSII. The freighter was not as helpless as it seemed and shot off a missle at the squad of Y-wings. Dash Rendar, who is kind of like Han Solo, tried to shoot the missle, but it's head was covered with something that deflected the shots. Half of the Y-Wings were destroyed when the misle exploded, 12 Bothans in all. That is what they mean by "many Bothans died". Hope that cleared eveything up for you.