Please be kind since it is my first topic I wanted to share with the world.

Are you asking a question or making a statement?

when exploring openings and strategies, I came across a notion that I wonder about for several weeks.

The defense is usually set up with either castling, knights or bishops and in endgames with pawns too.

To my surprise it does leave the attacking opponent with a big advantage: more pieces to attack with..

When someone castles kingside or queenside it usually leaves the king and one rook together. If the opponent does not castle or use another defensive action with rooks,knights or bishops, it means that that opponent has 1 piece more to attack with.

When the player uses a double / twin defense like 2 knights or 2 bishops the advantage grows.

... because at most levels of play (except perhaps the elite GMs) most players are poor defenders.  

That is because

• you have to consider more possibilities when defending than when attacking
• a mistake in defence is often more serious than a mistake in attack
• studying attacking methods and analysing attacking moves is more fun for most players than figuring out how best to defend.

@ Tigerprowl

First question: What is defense and what is offense?

I assume that defense is when you castle since you move the king to a safer spot behind a rook which protects it.

Offense is when a piece or pawn is moved with the goal to attack the opponent or a field on the board.

But attacking or defending is all in the eye of the beholder most of the time. Some say that putting a pawn on a3/h3 a6/h6 is defensive.

But when a piece of the opponent is on subsequently g5/b5 or g4/b4  would be considered as an attacking move?

Second question: How do you get an advantage if you don't check, take material, or mate?

Answer:

Moving pawns in a structure giving an opponent less room to manoevre on the board in is also getting an advantage.

At your third question:

”How is this labeled " defensive?”

Please re-read the comment I made:

"If the opponent does not castle or use another defensive action with rooks, knights or bishops, it means that that opponent has 1 piece more to attack with"

This is written as an attacking principle not defending principle.

if an opponent does not use a defensive move like putting two pieces (rooks/knights/bishops) as a wall in front of his/her king, they can use the pieces for attack, whereas the player who does use (rooks/knights/bishops) as a defensive wall does not attack with these two pieces since it would expose his/her king.

So the attacking player might not be able to attack the king directly, but has more pieces to attack the rest of the board with.

I hope that I cleared it up and gave a satisfying answer to your questions.

Why attacking player succeeds in chess....

Somehow you made me feel that a defensive player SHOULD win and attacking player should not. Like it would be inferior to attack or something. Personally I don't mind - I have attacked SO many times that I know how to defend as well. 

The purpose of my forum topic is to make people think about the piece advantage attacking players have to people who use a stationary rook after castling , knights/ bishops as defense.

I sincerely do not think either defending or attacking have any more positive points then the other. defending in most cases is harder to do than attacking.