Teasdale uses personification (a figure of speech in which a thing, an idea, or an animal is given human attributes) to contrast the beauty of nature with the horrors of humankind. Notice too, that Spring is specifically given the feminine pronouns “she/her” since spring is associated with renewal or creation. Consider also that “mankind” is never capitalized in the poem while Spring is capitalized here, which further emphasizes nature’s esteem and power.
"Spring herself, when she woke at dawn..."See in text(Text of the Poem)
This is an example of personification, which refers to instances of nonhuman entities and inanimate objects being given human charactersitics. Here, Spring is presented as a woman. As such, she will take little notice of the war waged by mankind. Nature will go on as it always has, and mans' conflicts will amount to nothing.
