Context

Tennyson wrote the poem on 2 December 1854, weeks after the catastrophic cavalry charge at the Battle of Balaclava (25 October 1854) during the Crimean War, reportedly spurred by a newspaper account of the action. A garbled order sent the roughly six hundred horsemen of the British Light Brigade charging directly down a valley raked by Russian artillery on three sides. The opening lines pitch the reader into that valley at the gallop, alongside the doomed riders.

How the repetition works

Phrasal repetition — a multi-word unit repeated adjacently, functioning more like refrain or incantation than single-word emphasis. About this distinction →

Where the catalogue's other phrasal repetitions hold still - Frost's 'miles to go' shifts meaning while the words stay fixed, Angelou's 'I rise' consolidates a claim - and Yeats's diacope 'Turning and turning' spins in place, Tennyson's tripled 'Half a league' drives straight forward. The dactylic gallop of the meter and the repeated phrase together imitate hoofbeats accelerating into the charge, so the repetition works as locomotion: each iteration is another stride covering ground toward 'the valley of Death.' It is the catalogue's clearest case of phrasal epizeuxis generating kinetic momentum - repetition not as emphasis or emotion but as the sound of forward motion itself.