Who said Ours not to reason why ours but to do and die.?

"The Charge of the Light Brigade" is an 1854 narrative poem by Alfred, Lord Tennyson

'Forward, the Light Brigade!'

Was there a man dismay'd?

Not tho' the soldiers knew

Some one had blunder'd:

Theirs not to make reply,

Theirs not to reason why,

Theirs but to do & die,

Into the valley of Death

Rode the six hundred