Fortresses

Fortress in chess.

This is a position where despite the stronger side having material advantage, it can't break through the fortress, meaning the defending side can hold a draw.

Carlsen famously stated he didn't believe in fortress during an interview. Yet he used a fortress position to hold the draw against Nakamura in a Armageddon game.

Here's the position Example 1

White cannot make progress. They agreed to a draw and Carlsen won the match ( Champions Tour Kiva 2020).

Now there are many different types just like in the real world , here's example 2

in this example, the white rook can swing from g3 to e3 and the king can go to f1. Black cannot make progress, White has established a fortress

In the next example, we don't feature a rook but knight and bishop :

Example 3: White to hold the draw.

Black can try to make progress but White can protect his pieces. Here's the position after Black tries to untangle white's pieces

Black can give a check on g1 and here's the next position after a few tries 

And like this castle, it is very difficult to break through. Actually the chess position is a fortress, White can save half a point !

Here's the final position from the same line :

if Black tries ..Qg8, then Nd4 and it is not possible for Black to break through White's defensive set-up. The game should end in a draw.

Question for the reader: Next position is Black to play. Is this is a fortress or Black shouldn't accept to draw the game despite being up in material,

Is this position (Black to play) a fortress ?