Tennyson's "Charge of the Light Brigade" commemorates the doomed charge of the British light cavalry on a heavily fortified position during the Battle of Balaclava (part of the Crimean War). This poem lionizes the cavalrymen and their charge as a feat of tremendous heroism.
Note, however, that Tennyson refers several times to the Light Brigade's charge as one which passed into "the valley of Death." Additionally, he explicitly states that "somebody blundered," in reference to the orders which they were given. Thus, even as he views the Light Brigade's members as heroes who remained steadfast in the gravest of circumstances, he is also well aware of the ultimate folly of that attack and the grievous loss of life which resulted from it. Even as Tennyson lauds the cavalrymen for their bravery, this moment is simultaneously viewed as a tragedy as well.