For the last three decades of the 20th century, Northern Ireland was mired in a toxic internecine conflict that came to be known as "the Troubles." Although bombings, assassinations, street battles and clashes with security forces claimed the lives of more than 3,600 people, it was an era defined as much by fear as overt violence.

There's a sense of dread percolating through "'71," a tense, confident thriller by first-time feature director Yann Demange. Set in Belfast in 1971, the film takes place just as the Troubles were reaching their destructive peak: nearly 500 people would lose their lives the following year, over half of them civilians, and quite a few of them at the hands of British soldiers sent to quell the unrest.

This is the milieu that greets Gary Hook (Jack O'Connell), a fresh-faced army private from Derby, England, who's surprised to learn that his squad aren't being sent off for a cushy tour of Germany. "I take it you all know where Belfast is?" says their commanding officer, only half jokingly, as he gives them their marching orders: "You are not leaving this country."