Dunkirk is an unrelenting film. I mention this first not as a positive or a negative but as a sort of fair warning. It is not a pleasant experience, though it is certainly something to behold. If you're looking for light summer thrills or you just don't enjoy the tension of a taut cinematic thriller, look elsewhere.

Even the first few moments of the film - superficially calm relative to the subsequent 100-plus minutes - are filled with dread. A handful of British soldiers amble their way through a deserted, shut-up town in northern France, scrounging for food and loose cigarettes. At some point during their travails, printed flyers flutter down from above. "WE SURROUND YOU," they say, and all at once the empty streets transform from seeming eerie to actually being perilous. This group is only allowed such free rein because the Wehrmacht is close and because the British Expeditionary Force is on the verge of being shattered. Bullets are about to fly.

Broadly, this is the kind of filmmaking we have come to expect from director Christopher Nolan - one of the craft's greatest working craftsmen. The inner core of his stories, shrouded in mystery, are always revealed layer by layer, extremely deliberately. The specifics of his latest picture make his ability to pull off that trick again a surprise, enhancing his already considerable mystique.

The nature of this particular story makes his usual conceit especially challenging. After all, the Allied evacuation of Dunkirk in late spring 1940 is a matter of historical record. It's not as well known as it should be in the United States, but the successful flight of more than three quarters of the 400,000 British troops caught in the pincers of Nazi Germany - an effort aided (by necessity) by all manner of small craft vessels crossing the English Channel - is well known enough that you can't do a dream within a dream or tell a story in full reverse or otherwise toy with time in quite the same way.

Nolan compensates for the constraints of history with laser-like focus, with a discipline in his storytelling that has certainly been missing lately, though, to be honest, I'm not sure has ever been this sharp or lean.

Rather than the sprawling war epic you might be expecting, you get an intertwined account of the evacuation from three perspectives - land, sea and air - and you never get a moment to rest. Not from the air, where three Royal Air Force pilots, among whom is Tom Hardy (yes, wearing a noticeably Bane-like mask) try to keep the mostly unmolested German dive-bombers from haranguing the amassed British troops on Dunkirk Beach or the vessels that will take them to safety. Not from the sea, where Mark Rylance is among the small-craft boat captains racing the 20-odd miles across the Channel to rescue anyone they can. And certainly not from the ground where newcomer Fionn Whitehead - the lone survivor from that pack of soldiers seen in the film's opening sequence - tries every trick in the book to get off the beach and get home.

It's an all-around harrowing experience, best embodied by Whitehead's character as he faces bombs from above and torpedoes from below, and one that does not let up because there is so little else that might offer respite. The dialogue is downright spartan, especially for Hardy and Whitehead. (Rylance and Kenneth Branagh, the Naval leader on Dunkirk beach, by comparison get a few more of the kind of war movie lines you might be expecting.) The German military is more of an unseen supernatural force of destruction than the physical representation of pure evil it typically is in other World War II films. You won't see the face of a Nazi soldier for the duration of the film. 

Hans Zimmer's score, meanwhile, experimental as it is in other Nolan films and underscored by the tick-tick-tick of a watch, never lets you forget that every moment is life or death. It, more than any of the actors, might the biggest star of the picture.

Nolan's last film, Interstellar, was both his most sentimental and free-wheeling - a father-daughter tale wrapped in hardcore science fiction that dabbled in everything from physics to climate change to time travel. I liked it, though I agree with the criticisms that it was often confusing and unfocused. To be more generous, it was a little bit too ambitious.

What a stark contrast Dunkirk is, grounded in historical fact, but also grounded in the reality of the situation on Dunkirk Beach - where nothing matters but mere survival. This is no small feat because a war movie so naturally lends itself to grandstanding. Instead, the blockbuster scale of Dunkirk lies exclusively in the five senses - in what the viewer can see and hear, and in what he or she can imagine you could touch or smell or taste.

This is a film filled with the five senses and so it has blessedly little time for much emotion - for context or backstory or anything that might give you the feeling of anything but relief when the shores of England are reached. 

This is Christopher Nolan at his very, very best.