300,000 soldiers trapped on the shores of Dunkirk. A rescue fleet comes from the north; Nazis from everywhere else. The soldiers know this. They also know that they have no say in whether they live or die. They can only wait.
Hans Zimmer uses the ticking of a pocket watch to signify the impending fate of the soldiers on shore; each tick represents one step closer to salvation or destruction, while its high speed increases the pace of the action. It is also figurative, showing the soldiers’ helplessness. Just as they cannot resist the inevitability of time, they cannot fight against their fate. They can’t control whether they live or die on the shores of Dunkirk.
The score also relies upon a distorted siren like that of a War of the Worlds’ Tripod, wailing away in an alien fashion. The siren shows the danger these soldiers are in: invasion from an all-powerful foe, one that they cannot hope to defeat. Together, they make this danger imminent and survival impossible, a far cry from the typical glorification of war. They are cutoff, isolated, helpless, slowly suffocating under the tightening noose of Nazi forces.
The score elevates the film, increasing the tension and the danger while also complementing the film’s own focus on time.