The Tower of London in this scene is both a practical stronghold and a symbolic one. It was simultaneously England's most famous prison, its main armory, the keeper of the Crown Jewels, and a royal residence. For Cade's rebels to attack it is to attack the physical infrastructure of royal power — not just a building but the central node of the state. Scales commands it with the pragmatism of a garrison commander who knows that a simultaneous rebellion inside the city and outside the walls is almost impossible to hold against. The fact that he sends his only available commander to Smithfield, leaving himself with apparently no reserves, tells you how thin the government's military resources have become. Every institution — the court fled to Kenilworth, the Mayor's forces broken at the bridge, the Tower besieged — is failing at once.