Describe the effect of the gunfire that was directed towards the charging British cavalry in "The Charge of the Light Brigade"?

In Tennyson's poem "The Charge of the Light Brigade," the gunfire that was directed toward the charging British cavalry is described as killing most of them.
We learn that there are six hundred British soldiers in the Light Brigade. Someone has blundered and ordered them to charge against the wrong artillery. They nevertheless attack bravely on horseback with their sabres out.
The gunfire is described as coming at them from cannons that are to the right of them, the left of them, and in front of them. In other words, they are being fired on with cannonballs from all sides. The enemy fire is also describes as hellish, and its effect is to "shatter and sunder" them.
Tennyson puts the best possible face on a military defeat that cost many lives, describing the men of the Light Brigade as fighting valiantly against great odds.