That which fortifies; especially, a work or works erected to defend a place against attack; a fortified place; a fortress; a fort; a castle.
(RQ:EHough PrqsPrc)
“… We are engaged in a great work, a treatise on our river fortifications, perhaps? But since when did army officers afford the luxury of amanuenses in this simple republic?(..)”
An increase in effectiveness, as by adding ingredients.
1979, Kiplingers Personal Finance'' (volume 33, number 7, July 1979, page 47)
Compare the nutrition information label of a regular ready-to-eat fortified cereal with that of a presweetened brand and you'll note that, although the sweetened one's sugar content is higher, the fortification is virtually identical.