How to Attack a Base in Minecraft - Outside the Base

1. Kill the person defending the base. He will be weakened, and you could get his/her weapons and their armor.
- You should do this from far away. If you get close up, you have a greater chance of dying, and if you do die, the guard can warn the people inside, and your whole raid could be ruined.

2. Intimidate them. Send Ghasts, Ender Dragons, Wither, Giants, or Zombie Horses outside the base.
- This might not be the best idea if you're looking for the element of surprise, because some of these enemies (Ender Dragons, Giants, and Zombie Horses) must be summoned, and the command appears in the server chat.

3. Destroy the walls. You could use cannons, TNT, or even a Creeper.

4. Enter underground. You could dig a tunnel underground, and then end up right in the middle of the enemy's base with the element of surprise.
- Use rails and minecarts to quickly traverse underground.

5. Enter the base and start the raid.