The use of simple and vigorous words in a farewell to arms reflects

The correct answer is:

The harsh and powerful reality of war.

A Farewell to Arms is a novel by Ernest Hemingway set during the Italian warfare of World War I.  Hemingway produces a genuine dialogue for his characters by using simple words and short, precise sentences. The novel is a first-person account of Frederic Henry, an American serving as a lieutenant in the Italian Army´s ambulance corps.

to force terrorists groups to stop attacking western targets using massive military force.