With the right application of spells, wits, and teamwork, even a small party of lower-level characters can handle what might seem like overwhelming numbers. But take one of those factors out of the equation and you might have a bit of a problem on your hands...
DM: As you round the corner, you are presented with an archway that is about five feet wide. Through the archway is what appears to be a large room, lit only by a small cooking fire about 15' away from the entrance. In the glowing light of the fire, you can make out a large number of smaller, dog-faced creatures. [rolls] Having expected to find the main kobold lair in this general vicinity, you are not surprised. [rolls] But the kobolds are taken completely by surprise at your sudden arrival! Apparently one of them was telling such a good story to the others that they missed the sounds of your approach entirely. You will get one free round before we have to roll initiative.
Groin: How many kobolds do we see?
DM: You can't be 100% certain because of the lighting, but at a quick glance you can be sure there are at least ten, though there might be more.
Groin: Well, we should still be able to handle them as long as we play it smart. Angora and I will take position on this side of the doorway, side-by-side. With his sword and my axe, we should be able to keep a minimal number of them attacking us and at least not get overwhelmed. Bore'me will prepare a vial of flaming oil to toss over our heads once they engage us; hopefully that will catch a few of them as well while it prevents them from pressing their front line. Then he can toss a heal our way if one of us needs it. And Eggoless can cast sleep centered on one of the kobolds near the fire right now so tha...
Eggoless: That might not work.
Groin: What? Why not?
Eggoless: I didn't prepare Sleep for the day. I prepared Detect Magic, instead.
Groin: Wha... What??
Eggoless: Well, last time we had that magical dagger in our possession and didn't know about it until we got back to town and had it tested, so I wanted to be able to cast Detect Magic in case we found any other treasure that might be magical!
Groin: Oh, for Pete's sake...