A question that has been on my mind for a while. I was reading over your Laboratory of Politics piece on Volantis. Given that the source material notes both a massive salve majority and a military made up of slaves, what keeps the Old Blood or the free population in power exactly? What is there to maintain the monopoly of violence for the free population if they do not make up the military? It seems like the masters would not have any real recourse to rebellion given these conditions.

Well, we learn a number of methods that the Volantenes use, many of which are culled from historical slave societies:

1. Exemplary punishment to inflict terror. Hence the heads on the Long Bridge, and the use of the army against freedmen disorder. 
2. Lots and lots of safety valves. Religion, manumission, entertainments (remember all the electioneering), and I wouldn’t be surprised if there were also policies of allowing slaves days off to work on their own account, maybe even wages, etc. 
3. Use of cultural practices to divide slave from slave and prevent solidarity. We see this with the soldiers – “The slave soldiers of Volantis were fiercely proud of their tiger stripes…what are they, if not tigers?” – but I’m sure there’s an established hierarchy within the ranks of civilian slaves as well. 
4. Use of cultural practices like the mudsill theory to foster unity among non-slaves. Although they don’t do this as much as they ought (what with the Old Blood), in Volantis “even the vilest beggar stands higher than a slave.”