What does the poem seem to say about the relationship between nature and human beings?
The natural world is shown to be one that does not stop with the temporal condition of human beings. Teasdale is a pacifist and understood that the aggressive tendencies in human beings to settle differences through militaristic ends is contingent, at best. She understands that while humans in such a condition might view their actions as life altering and transcendent, actions like these are actually far from it. Teasdale's point of emphasis in the poem is that the natural world will not necessarily stop from its function despite what human beings do. If humans seek to destroy one another through their own hand, nature will move on and continue, even if human beings do not. This brings about a sense of understanding and perspective about the temporal nature of human action.
This is seen at several points in Teasdale's poem. The "frogs in pools" still sing their song. The "soft rains" will fall. The songs that the robins sing reflects a state of being in which "not one of them will know of the war" and "not one will care at last when it is done." The continued emphasis of "not one will mind" is only underscored at the end of the poem in which nature, in the form of Spring, will "scarcely know that we were gone." Nature is shown to be the transcendent force, one in which humans occupy a small role. This illuminates a temporal relationship and a contingent state of being between people and the natural world.