Doesn’t it seem odd that Janos Slynt became Commander of the City Watch? He’s a lowborn son of a butcher, holding a position that’s usually given to noble younger brothers and knights and such (Daemon Targaryen, Addam Marbrand, Jacelyn Bywater, even Moryn Tyrell for the Oldtown watch) so how did he gain the position? Can bribes and threats really carry such a man so far?

It didn’t have much to do with bribes and threats. Janos Slynt was Commander of the Iron Gate, and was promoted when his highborn commander, Manly Stokeworth of House Stokeworth, died. It’s likely that this happened right after the Sack of King’s Landing, where a lot of the nobles who would normally hold posts in the Gold Cloaks were invalidated by their support from the Targaryens, so Jon Arryn promoted from within.