The Charge of the Light Brigade
There's not a whole ton of plot in this poem, but in our opinion, that's a good thing. Tennyson doesn't bog you down in the history of the Crimean War, or describe the events leading up to the Battle of Balaclava (see "In a Nutshell" for more on that). He just throws you into the middle of a battle, giving you a vivid sense of the moment.
What's the moment, you ask? Well, basically, the 600 horsemen of the Light Brigade are ordered to charge forward into a valley, with guns on all sides. They do, and they meet heavy fire. When they encounter their Russian enemies, they attack them, kill some of them, and then retreat down the valley. The gunfire on the way back is just as bad, and many of these heroic soldiers die.