In Ridley Scott’s “Body of Lies,” Leonardo DiCaprio is Roger Ferris, a Farsi-speaking CIA agent resigned to a divorce, running all over the Middle East and sparring with his boss, Ed Hoffman — a corpulent, amoral realist who, as played by Russell Crowe, delivers kill orders while he watches one of his kids playing soccer back in safe and secure D.C.

Smart, cynical and ruthless more out of necessity than by disposition, Ferris identifies himself as a “political adviser.” If he has a lesson to learn, it is that no one he deals with is entirely innocent, even a contractor he sets up as bait for a larger fish — an al-Qaeda operative with an advanced degree from that Tarheel school in North Carolina.

Scott, who gave us “Blackhawk Down,” another gritty but lesser war movie, seems to be out to demonstrate that the integrity of our entire operation in and around Iraq is mired in a grisly and gruesome maze inhabited by spies, terrorists, counterspies and other assorted operatives who could turn on you in a second.

In more than one scene, we observe confrontations in the desert and in crowded neighborhoods; they are seen live back in Washington, thanks to a satellite overhead. In one of the most telling encounters in a movie that is smart and sizzling with action, the Americans are outmaneuvered by terrorists who stir up mounds of dust as they encircle a pickup in their Mercedes SUVs. When the four vehicles depart in separate directions, Hoffman can only guess which SUV has snared his man.

On alien ground

While we are not told anything new about those who want us dead, “Body of Lies” drives home a theme worth thinking about. Spies, counterspies and foreign intrigue are not novel topics, but what still may strike us as different is the realization that we are not dealing with people who share our traditions — friends and enemies alike. Whether we are in Iraq, Turkey or Jordan, it comes down to one question: Whom can you trust?

From there it’s on to an answer provided by the movie’s title. “Never lie to me,” Mark Strong’s Hani Salaam tells Ferris when they first meet in Jordan, where Salaam heads that country’s intelligence division. Yet, as we will observe, lies are all but inevitable, even among allies. In the process, lives are not only at stake but deemed dispensable for a higher good.

“Body of Lies” swirls in a vortex of amorality where each side considers itself righteous. “We have bled and now they will bleed,” says al-Qaeda’s cell boss to his adherents. It’s a high-stakes game in which we as viewers realize from afar that our lives, too, may hang in the balance. It’s no new revelation, but as realized in this action-laced movie penned by “The Departed” screenwriter William Monahan, the danger is more than palpable.

If we race along with the action, we can savor some incidental pleasures with shafts of witty dialogue. Referring to our high-tech wizardry, Crowe’s agent tells Salaam, “You invented algebra; we’re the guys who found out how to use it.”

Along with Matt Damon, DiCaprio has solidified his claim as a top-notch action hero — gritty, credible and a touch vulnerable. Who would have thought about this dimension when we were enjoying both of their work in movies like “Good Will Hunting” and “This Boy’s Life”?

Bonus performance

The movie’s extra-special bonus is the work of Mark Strong, who all but steals the show. At first, I thought it was Andy Garcia in the role of the Jordanian, but Strong blows this notion away with a great, career-defining performance. His name is sure to surface come award time. A familiar name in Great Britain, Strong is the son of an Italian father and Austrian mother. His birth name is Marco Giuseppe Salussolia.