Another sutta based upon a very fine simile. I can't help thinking that perhaps these are intended for those followers who have a metaphorical cast of mind. Those who grasp a holistic symbol or idea first, and then use it as a reminder of the specifics that it elucidates, rather than those who are happy with the linear account of consecutive items. And they are often good literature, in that the parts of the simile (or metaphor) can be pushed quite far. When the Buddha describes the different hindrances, for example, as being like bowls of impure water, or like the vicissitudes that can befall a householder, I have often been struck by how apt these comparisons are. And it all goes to show that even warfare and danger has something useful to offer us.
I find these similes really helpful. Often on these pages people get bogged down in a type of battle over definitions and meanings that is rather like lawyers looking at statutes and case-law. But here we have the Buddha saying, in effect: "Can you imagine this? Well, mindfulness is like that..."
This one has an interesting set of qualities, but it is really just the Panc'Indriya plus Hiri-Ottappa and hearing and recalling the true Dhamma. These latter two are inserted into the more familiar list of Faculties, and concentration is separated out and treated as analogous to the food consumed by the fortress. The fact that it is treated as food, rather than the requisites of warfare, is quite telling. The other qualities will enable one to make progress, to defend the ramparts and kill one's enemies. But the Jhanas are there for ease and comfort, for sustaining one in whatever one does. Thanissaro often talks about this, as does Ajahn Sucitto. Meditation should feel good. Sucitto often teaches meditation as being to do with a sense of fulfilment, of being replete, or whole. With this feeling, we can do the other bits of the practice which might otherwise feel difficult and unrewarding. Without being well-fed and happy, it is difficult to defend the fortress. As Napoleon famously said, an army marches on its stomach. (And leading the French army, he surely would have known!)