What they knew
From high ground, the British commander Lord Raglan could see Russian troops removing captured British guns from redoubts. Down in the valley, his cavalry commanders could not see what he saw.
The choice
Raglan sent a written order for the cavalry to advance rapidly and prevent the enemy carrying away the guns. It was carried by Captain Louis Nolan, who was impatient with the cavalry's caution.
Lord Lucan asked which guns. Nolan is said to have gestured broadly, toward the far end of the valley, where Russian artillery was positioned, not at the redoubts Raglan meant. Lucan ordered Lord Cardigan, his brother-in-law and bitter rival, to attack.
The consequences
The Light Brigade charged down the valley under fire from three sides, reached the Russian guns and was forced back. Nolan was killed early in the charge. Of roughly 670 riders, about 110 were killed and many more wounded. It became the classic example of how a decision can fail in the gap between the person who makes it and the people who carry it out.