Literary Devices in The River Merchant's Wife: A Letter
Here's where the poem's structure first suggests that it's a letter. In the first five stanzas, she provides a summary of her relationship with her husband, the "you" of the poem, even though he knows all of this already. It seems written for the reader's benefit, not his, and only in the last stanzas begins to sound like a letter written to him. It could be that the final stanza alone functions as a letter, with the previous six examining her reasons for writing it.
Here it's important to note that Pound didn't write "The River Merchant's Wife" but rather translated it from the original Chinese, written by Li Po. Li Po's natural images and Eastern sensibility would've appealed to Pound as one of the founding members of Imagism, a movement in poetry dedicated to clarity, rhythm, and precision in diction. Pound's translation is one of the most faithful and well-known, with the only major change being the title, originally written as "Chang'an Memories."