The Charge of The Light Brigade?

[jellytot01]

Why does Tennyson use so much repetition in this poem?

[Peter Pedant]

I had nt realised he had.

I think it is to reproducein the poetry the rhythm of  the gallop of the horses too

[jno]

half a league, half a league, half a league onward... You can hear the horses galloping behind that.

[spookylad]

Repetition is usually used to emphasise an idea or an image, or to build a very strong, pounding rhythm. In this poem, Tennyson uses it to give a strong sense of movement, urgency and inevitability.

[cootchiecoo]

it could also be considered as well as the two good points above as a structural contradiction. The jaunty song like effect of repetiton is juxaposed to the message that is finally delivered about the needless slaughter of most of the soldiers.
Is just my interpretation anyway, hope it helped!