You searched for: “fortressing
fortress, fortresses; fortressed, fortressing (verbs)
To protect by or to furnish with a strong defensive structure: "Many geographical areas in history have fortressed their villages, towns, etc. so they could protect themselves from invaders who wanted to steal their property and even force them into slavery."

"The people felt the need to fortress their town by constructing a fortress so they could defend themselves against attacks by wandering groups of thieves and killers."

This entry is located in the following unit: fort-, forc- (page 3)