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'Master, what's the deal with calvary'

'Young Padawan, calvary deal double damage after a charge, but can not
assault fortifications with siege engines.

and not

'Young Padawan, calvary are great in the open field but don't use them
if we're assaulting a city'

The first is just stating fact so the student can come to his own conclusions.

The second is a suggestion, and implies the student will be punished
if he doesn't follow it.

-- 
"Growth in wisdom may be exactly measured by decrease in bitterness"