Thanks to the widely seen dramas “The Killing Fields” and “The Deer Hunter,” pictures of the nightmarish fall of Saigon and the subsequent evacuation of the U.S. embassy in 1975 are burned into our collective cultural memory — pictures of thousands of desperate South Vietnamese trying to crawl up embassy walls, of mothers throwing their babies into helicopters.

In “Last Days in Vietnam,” documentary filmmaker Rory Kennedy dusts off those memories — some of them willfully blocked — to reveal the recollections of those who were there. With help from some recently found Super-8 footage shot aboard an American ship, she has crafted a factual recounting of heroic efforts accomplished amid unrelenting pandemonium, sometimes in direct defiance of orders from home.

Kennedy, a daughter of Robert F. Kennedy who has received previous accolades for her films “Ghosts of Abu Ghraib” and “American Hollow,” begins the doc with background context. After the failure of the Vietnam War and the resignation of Richard Nixon over Watergate, the American public was disgusted with its government’s deception and not about to approve the $722 million in aid to South Vietnam sought by President Gerald Ford. The emboldened North Vietnamese escalated their territory takeovers until the U.S. decided it had no recourse but to remove all American personnel.

To do this required subterfuge via radio signal so as not to panic the South Vietnamese. The code to begin final evacuation culminated with Bing Crosby singing “White Christmas.” It’s instantly chilling to hear that benignly sentimental song while watching a montage of the despairing, panicked faces of some of the thousands of Vietnamese who would eventually ring the embassy in hopes of salvation.

“Did the right people get out? A lot of them just happened to be good wall jumpers,” says one source.

Nearly 40 years later, what ultimately was a massive betrayal to those left behind clearly still weighs heavily on many of the military and CIA interviewees who had developed deep bonds with their South Vietnamese counterparts. One said he even “dreamed in Vietnamese.” Even after the “enough” dictum came from Washington, these men whose own lives were in peril kept pushing South Vietnamese into Marine helicopters making back-and-forth runs to offshore ships.

Kennedy gives Henry Kissinger, then secretary of state, more of a pass than those who believe him guilty of war crimes over bombings in Cambodia will think he deserves. He comes off in a sympathetic light, citing the U.S. government’s two primary goals — to save as many people as possible, and also to save “the honor of America,” so the nation wouldn’t be seen as stabbing the South Vietnamese in the back.

The doc is at its best when reporting what is no doubt the least-known aspect, in this country, of the evacuation — the bravery of the South Vietnamese soldiers and pilots who landed helicopters in their own back yards to gather up their families and friends, then headed out to sea with no certainty that the departing U.S. carriers would let them land. The Super-8 footage, found undeveloped in the attic of a serviceman who had been aboard the USS Kirk, shows some of the dramatic landings of aircraft overflowing with people, after which the copters would be pushed into the water to make room for the next one.

“Last Days in Vietnam” should be used in high school and college history courses to foster a deeper understanding of these gut-wrenching days, but also as a testament to people, as one source puts it, “doing their best under terrible circumstances.”