McChrystal's boss takes over as US commander in Afghanistan

General David Petraeus, the head of US Central Command, has replaced General Stanley McChrystal as commander of US and Nato forces in Afghanistan, following the latter's removal. Petraeus is widely seen as being instrumental in turning around US fortunes in the Iraq war, and many are waiting to see if he can he do the same in Afghanistan. Al Jazeera's Patty Culhane reports.
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