Complex sentence: The Senate authorized the Morgan Report which after two months of hearings of witnesses under oath and with cross examination, found Blount's conclusions to be mistaken, much of the testimony he gathered recanted, and cleared the military and Stevens, of blame.
Split into simpler sentences: The Senate authorized the Morgan Report which conducted two months of hearings taken with witnesses under oath and under cross examination. The Morgan Report Blount's conclusions to be mistaken; much of the testimony gathered in the first report was recanted, and Morgan cleared the military and Stevens of blame.