Charles's cautious failure to directly assault the town, putting a higher priority on minimising losses than on victory, had cost the Royalists dearly; while claims for their number of dead and wounded men ranged from 1,000 to 1,500, only around 50 people inside the city were killed. Essex's force, on the other hand, was in relatively good shape; its one issue was the lack of supplies. If he stayed in the Severn Valley, Essex would be unable to get reinforcements or outside aid, the London elements of the army would demand to go home, and the one remaining significant Parliamentarian force would find itself pinned down, while Charles, with secure bases at Oxford and Bristol, would be able to starve them into surrender while other Royalist armies ran rampant through Britain. Because of this, Essex had no choice but to try to return to London. Travelling back across the Cotswolds, as he had done to reach Gloucester initially, would expose the Parliamentarians to Charles's cavalry on open ground.