Tostig's Assassination of Harold

Tostig, his wife and a number of their thanes and officers were exiled from england. And upon this exile, tostig's feud with his brother such that it was became murderous. The records imply that tostik blamed his brother for his recent fall from power. But onestly, it's difficult to imagine what harold could have done to prevent this exile. I mean, he was powerful, but he wasn't a god. Even if we assume that edward was too weak and he was too sick to do much, and that harold was basically ruling in all but name,. i'm not sure what tostig expected harold to do about it