In early 1915, the Frost family made a hurried departure from England as the war in Europe escalated. Despite fresh memories of the Titanic tragedy, Robert and Elinor Frost were undoubtedly more concerned about German U-boats than icebergs on the trip home aboard the SS St Paul with their four children. Although they successfully escaped the ravages of World War I, at the time the most mechanized conflict in history, the Frosts returned to a country undergoing its own rapid and irreversible changes at the hands of technology.

The potentially destructive effects of machinery and technology were clearly on Frost's mind in Mountain Interval. Some of the violence he depicts is directed toward humans. In the poem “‘Out, Out—’” a young man dies when a momentary lapse of attention while operating a buzz-saw severs his hand; that is, while the young man is sawing limbs of trees, his own limb—and life—are lost. And in the poem “The Vanishing Red,” a more primitive technology, a water-driven millstone, is used to crush a Native American man who is pushed into the wheel pit by the mill operator who acts upon an impulse of disgust toward someone of another race.

Most of the violence in Mountain Interval, however, is directed toward plants and animals. In “The Exposed Nest,” the cutter bar of a tractor makes a clutch of young birds even more vulnerable to their predators and the environment; in “Christmas Trees,” we must contemplate the death of one thousand young trees by a businessman who wants to buy them for a paltry sum to enliven but briefly the homes of city-dwellers; in “Pea Brush,” we see and smell birch trees “bleeding their life away” to serve as supports for young pea plants; in “Range-Finding,” a stray bullet tears a cobweb, destroying the careful work of a spider and narrowly missing the nest of a ground bird. In the poem “The Gum-Gatherer,” a man engages in the serial scarring of trees to collect and sell the resin they produce for their own protection; in the poem “The Oven Bird,” a bird chronicles the diminishment of his habitat by dust-raising automobiles and landclearing development.