Why does the poet repeat a line or phrase three times in stanza 1 and stanza 3?
Repetition is a technique that many poets use to great effect. Some of the reasons poets use repetition are to enhance the lyricism of the poem, to create cohesion within the poem, and to reinforce the meaning of the poem. Two specific types of repetition used in poetry are a refrain and anaphora. A refrain repeats words between stanzas; anaphora repeats the same words at the beginning of subsequent sentences or clauses. In Alfred, Lord Tennyson's poem "The Charge of the Light Brigade," he uses both types of repetition to create the three effects noted.
In stanza 1, the words "half a league" are repeated three times in succession. This is a type of anaphora. This repeating phrase increases the lyricism of the poem, that is, it makes an appealing sound to our ears. Because the phrase has a special rhythm, called dactylic, it is especially pleasing. This same rhythm is repeated in each stanza, lending cohesion to the poem, helping it hold together as a unit. The dactylic rhythm gives the feeling of riding horseback, and that reinforces the meaning of the poem. To repeat "half a league" three times helps the reader get the feeling of being a cavalryman on horseback getting closer and closer to to desired destination.
In stanza 3, the words "cannon to right of them, / Cannon to left of them, / Cannon in front of them" are mirrored by the similar but slightly different words at the beginning of stanza 5: "cannon to right of them, / Cannon to left of them, / Cannon behind them." Again, this is anaphora. The dactylic rhythm and anaphora continue to be pleasing to the ear while connecting the stanzas to each other. Here the repetition reinforces the meaning of being surrounded by the Russian artillery that bordered three sides of the field the brigade was charging across. The repetition makes readers feel as if they are in the middle of the battle, too. Imagine just saying, "They were surrounded on three sides while charging down the hill." That conveys the meaning, but not the feeling, of being in the battle. The use of repetition allows the reader to enter into the scene emotionally and with the five senses.
The anaphora at the beginning of several stanzas balances out with the refrain at the end of each stanza that refers to the "six hundred" in one way or another. This again enhances the lyric quality of the poem while tying the stanzas and the entire poem together. Thus repetition is a key technique Tennyson uses to immortalize a battle that otherwise may have been lost in the pages of history.