James Cameron’s Aliens (1986) celebrates its fortieth anniversary this July. For generations, the groundbreaking action-horror masterpiece has won over fans with its effortlessly quotable band of hard-up marines and its fierce, iron-willed protagonist — Sigourney Weaver in the role of Ellen Ripley.

However, Aliens has also been divisive. Critics like Pauline Kael, Roger Ebert, Sheila Benson, and Richard Schickel were split over how to interpret the film’s then-curious mixture of action and horror. Even those who praise its undeniable thrills and action chops regard it as the mere crowd-pleaser sequel to the far artier original film, Ridley Scott’s Alien (1979).

Writers have also been obsessed with reading secret political messages into the movie. Aliens has been cast as everything from a detailed work of Marxist theory and a subversive queer allegory to a Reaganite attack on immigrants and a defense of civilian massacres during the Vietnam War. But the movie doesn’t need a magic cypher; it’s all right there on the surface. It’s a working-class epic — monsters, machine guns, and all.