fortify

ˈfɔːtɪfʌɪ

verb

provide (a place) with defensive works as protection against attack.

the enclave has been heavily fortified in recent years

build defences round,secure,protect,surround,embattle,rampart,mound,strengthen,reinforce,toughen,consolidate,bolster,shore up,brace,buttress,stiffen,support,hold up