All the world wondered. (line 31)
Tennyson does a cool thing here (at least for poetry dorks like us). Without quite letting us know that he's doing it, he expands the Light Brigade's audience. Suddenly it's not just the folks on the battlefield, but the whole world that watches them. It's almost like they are instantly famous, as soon as they start the charge. He could have said "the Russian soldiers wondered" or something like that, but instead he blows it up. The point of this poem is to make these men famous, and he gets started right away.
While horse and hero fell. (line 44)
Maybe calling these men heroes seems obvious, but Tennyson waits a long time before dropping that particular word. We think that gives it even more impact. Remember, the idea that these men are heroes isn't just one theme of the poem, it's the whole point. This poem is meant to turn these men into heroes, or maybe to publicize their heroism. Having the poet laureate of England write a poem about you is pretty awesome PR, especially at this time.
When can their glory fade? (line 50)
Glory is a key word here. That's the ultimate respect and reputation that a soldier could hope for. To have people respect you is one thing, but to have glory coming out of you like a shining light, well, that's pretty cool, isn't it? This, by the way, is a great example of a rhetorical question. The answer of course is "Never."