What you'll learn
How to get defense up so you can get ready to pump some units out.

Settings

Game Type: Regular
Civilization: Anything but the Persians, Franks, or Goths.
Team: 1
Difficulty: Medium or Hard
Other Players: 3
Map Type: Anyone. I suggest Forest maps
Map Size: Medium through Large
Resources: Standard
Population: 200
Reveal Map: Normal
Starting Age: Dark Age
Computer Players: 3. One on your side the other two teamed.
Team Together: Checked
Team Lock: Checked
All Techs: Unchecked
Record Game: Checked

The recorded game (optional)
Sorry. I don't post recorded games.

Here are some of the benefits from defensive strategy.

Harder to Stop:
Whoever you are fighting with won't be able to get into your base without a big load of siege weapons.
Which means they will never be able to destroy your economy or hurt your unit production. All you have to do is make sure that wall stays up.

Mixing and Matching:
If you mix this strategy with the Villager Boom you would basically be unstoppable. You would have economy and defense on your side. 

Note: Before reading on know that "TC" stands for Town Center

Kick It In Gear Daddy.
Your goal in the early stage of defensive strategy is to hit the Feudal Age fast but keep up your villager population.

1.) When you start off basically start with a Villager Boom
2.) You will rapidly progress from a small economy to a bustling economy
3.) You will make it into Feudal Age in under 15 minutes.
4.) Make sure you have lots of villagers mining stone its important.
6.) Build a market so you can sell extra gold, food, and wood for stone.
5.) Now the fun begins

This Piggy Built A Imperishable Stone Wall
Your goal now is to put a big fat stone wall around your base in as little amount of time as possible

1.) Select about 5 villagers and hot key V than click Stone Wall.
2.) Put it around your city
3.) Once they are done you should put a gate in so you can let your troops get out when things get rough.
4.) Now, spectate 2 directions in which your enemy would come. Put around 4 towers in each direction.
5.) Next, place 2 towers in every other direction. I would guess you have about 12- 16 towers.
6.) Now mine stone like hell. If you run out of mining or don't have enough sell the extra stuff.
7.) Make sure you are pumping out an equal amount of units to defend your wall if they bring siege equipment.

Unusual Upgrades
You are making your defense happen. You can survive a lot unless they double team with Siege Equipment they most likely won't in this amount of time though. 

1.) Now, hopefully you have hit Castle Age.
2.) Once you have you need to upgrade to Fortified Wall and Guard Tower.
3.) You need to build a university if you haven't because you are going to need it for upgrading those towers.
4.) Now you are getting stronger

When they attack do as the attackers
This if for when they finally decide to come try and give you a whooping.

1.) If they do attack have men on extra. All varieties. To fight anything from archers to siege equipment
2.) If they do start whooping you with siege equipment use a lo of villagers (5 - 12) to fix the walls and towers.
3.) But at the same time be pumping out infantry and calvary because those walls can't hold forever.
4.) Next, go out there after they are worn out some from the towers and you stand by units and give them a whooping
5.) A good strategy to use could even be Skirmishing

Winners Can Think
I really have told you no way to win with the defensive strategy. It's really just a way of staying in the game.
So you have to win your self. There are lots of different ways to win though and I'll be posting some soon.