Copenhagen Hnefatafl tactics

[Draganov]

Hello tafl warriors,
I am going to explain some basic tactics regarding Copenhagen Hnefatafl. I hope my comments will help players to imrpove their playing skills.
Some of the principles have been already formulated by Tim Millar (Crust) but his website is not active anymore, so I think it is good to be mentioned again here. Some of the tactics are my own explanations based on my game experience.

HOW TO PLAY WELL WITH BLACKS

Here are the main goals of the blacks:
1) Block the corners with some sort of barricades.
2) Be careful of not opening much space on the sides where the whites could create an exit fort.
3) Create a cordon (indestructable line of 11 black vikings) and gradually reduce the space on the board.
4) Capture the king.

First and most important goal for the blacks is to try to block the corners as soon as possible. The king in the beginning of the game is placed in the center surrounded by his army. It is not easy to capture the king while he has so many vikings to protect him. That's why the blacks must not try to attack the king too early in the game but instead of that, they need to focus on blocking the four corners.

HOW TO BLOCK A CORNER WITH A BARRICADE

Look at this diagram. This is how fully blocked four corners look like:

Fully blocked corners

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To achieve blocking a corner, blacks will need at least 3 moves as it is shown on the image below:

Moves to block a corner

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However, the whites could respond to these three black moves by attacking another corner or by placing one of their own vikings in the corner. So, when playing as black, it is not safe to concentrate all your resources on one corner because white will simply go to a less well defended one.
Sometimes blacks will not be able to block a corner with only three moves and they will need to use more complex barricades like shown below:

Complex barricades

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These four barricades are just as effective as the one shown previously, but slightly less efficient, in the sense that they each require four warriors instead of three.

[Draganov]

In some games, whites could be able to infiltrate a warrior into a square near the corner as shown below:

Most complex barricades

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Here blacks will need to use really complex barricades to secure the corners.
It may not look like it at first, but black has got all these corners secure, even though white has managed to gain a foot-hold in each corner.
The reason is that the white king cannot jump over his own warrior, so that warrior must move out of the way, before the king can reach the corner.
As soon as the white warrior moves out of the way, black can easily close up the gap behind it, sealing the corner off securely.
This is a very good example of a fundamental principle of black hnefatafl strategy: use the fact that the white warriors get in the king’s way!!! You’ll find sometimes that the only thing stopping the king from winning the game is that one of his own warriors is between him and the corner– even if you can capture that warrior, it might be better to leave him there, or even block him in so that he can’t move out of the way.

[Draganov]

Another complex barricades are shown on the image below:

Most complex barricades

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Here Jrton80 (blacks) has beautifully blocked all corners against Draganov (whites). Look at the upper right corner where whites have 3 vikings close to it. However, blacks managed to block them by something similar to a fort construction (vikings on g11, h10, i10 and j11). If the whites move j10-k10 then the blacks will play j11-j10 reaching another kind of barricades.

The bottom right corner is also secured since blacks can achieve a similar blocking fort with the moves k6-k2 and j5-k5. Their viking on h1 can move to i1 immediately if the whites move out their viking from i1 to somewhere else.
These kind of barricades are not as secure as the previous ones but are very difficult to be broken by the whites.

PS) To see how the game between Draganov and Jrton80 continued you can search in the game archive for this game:
Draganov / Jrton80. Tournament 280, Copenhagen Hnefatafl 11x11, 72 moves, 2022-01-27 12:21:35, white won (Draganov)

[Draganov]

Sometimes blacks will not be able to block the corner with a barricade but could create difficulties to the white king to reach the corner. A useful defensive formation is called "The Tower". It consists of 4 vikings arranged in a square like it is shown in the image below:

The Tower

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In this position whites (Draganov) managed to place a viking in the upper left corner (A9). Moreover, the blacks (Death) didn't manage to create a barricade and to neutralize this viking. However, they succesfully built a defensive tower that really prevented the king to reach the corner.
Four warriors arranged in a square like this are indestructible. Of course, as soon as one of the four warriors moves, the tower becomes vulnerable to attack.
The tower could be used by blacks to block access to a corner or to disrupt the whites attempts to create an exit fort.

PS) To see how the game between Draganov and Death continued you can search in the game archive for this game:
Draganov / Death. Copenhagen Hnefatafl Bell 11x11, 129 moves, 2022-02-23 16:56:22, white won (Draganov), timing x10

[Draganov]

Let's see another black's tactics to block the king on the edge of the board. In some situations the white king will come really close to the corner but will be left without support from his warriors. Then, the blacks have the opportunity to trap him on the edge and after that they can focus on killing the remaining white vikings without any risk of defeat.
The whites must be really careful to avoid positions like these below:

Trapped next to the corner

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Here the blacks managed to trapped the king next to the corner. The viking on k2 is practically immortal since the king cannot move. So, the only way for the whites to escape from this position is to organize a shieldwall capture and kill the vikings on K4 and K5. However, with few white vikings left, this task seems practically impossible.

Another similar situation is shown on the image below:

Trapped on the edge

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Now, the black viking on K3 could be killed by the white's move J2-K2xK3, however, the blacks can also capture the white viking by the move G3-K3xK2 and the king will continue to be trapped. The viking on I1 is guarding the viking on I4 waiting to kill every single white viking that tries to step on H3. The situation for the white king is not optimistic at all.

On the image below, you can see how the Tower technique could be used to trap the king on the edge and although the king has little space to move, he cannot escape from this trap:

[Draganov]

Let's examine another blocking technique that could be used by the blacks to defend the corners. I call it 'Defence Line'. It consists of at least two vikings placed next to each other in a line and blocking the movement of the opponent's viking or king.
Look at the examples below that were taken from the game between Draganov (whites) and Alex Hnefatafl (blacks). The whole game could be searched in the game archive by this information:
Draganov / Alex hnefatafl. Tournament 280, Copenhagen Hnefatafl 11x11, 82 moves, 2022-01-27 12:21:35, black won (Alex hnefatafl)

Blocking an exit path

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Here blacks played K10-I10 blocking the viking on I11 and not allowing him to open a path for the king. The black vikings on J8 and J9 are forming a defence line, which stops the white viking on I9 to reach the right side of the board and attack from behind.
The game continued with the moves I11-J11 followed by black's response I10-J10 forming another defence line that blocks the viking on J11 as shown on the image below:

Defence line by 3 vikings in a row

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After the moves I9-I7 and J9-I9 the whites tried to open a path for the king by playing J11-I11 but the blacks responded with J10-I10 forming another defence line as shown on the image below:

Defence line by 2 vikings in a row

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[Draganov]

After couple of moves, the game reached a position in which the blacks (Alex Hnefatafl) used 'the Tower' defence to trap the king on the edge. This game is a true masterpiece showing great understanding of two defencive techniques- 'the Tower' and 'Defence line'.

The Tower used to trap the king

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[Draganov]

In one of the previous posts we saw how Jrton80 implemented a structure similar to a fort but used it as a defensive tool. Let's see more of this technique. On the image below Floki (whites) managed to create a strong attack to the bottom left corner. However, Draganov (blacks) answered it with something like 'Inverted Fort'. See the image below:

Inverted Defensive Fort

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If the whites move the viking on A3 out of the king's path, the blacks will simply play A2-A3 closing the gap. This kind of fort could be easily destroyed by the whites if the blacks didn't have vikings on B9 and H3 who are watching carefully and are ready to help the fort formation in case the whites attempt guillotine attack.

After couple of moves, the position reached one of the previous mentioned barricade structures. See the image below:

Flock Formation

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The vikings on C3, D2 and D3 are creating something that I call "Flock formation" because it reminds me of a flock of birds. I am going to examine this formation in more details later.
In the end after several moves, the game reached another interesting position where Draganov (blacks) managed to defend a corner with defensive fort. Look at the image below:

Devensive Fort

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These kind of defensive structures could be broken by whites but they could slowen white's attack and safe blacks valuable time to organize their defence in a more accurate way.

PS) To see this example game search in the game archive for:
Floki / Draganov. Tournament 459, Total Hnefatafl 11x11, 56 moves, 2023-02-11 23:50:09, black won (Draganov)

[Draganov]

In the previous post I mentioned the 'Flock formation'. It could be very useful for blacks to slowen whites attack and to build a defensive line between the king and a corner or between the king and his warriors isolating either the king or the warriors depending on the goal.
Let's see some examples of the 'Flock formation' in the image below:

Flock formations

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The examples were taken from the game:
Draganov / Cacreal. WTF World Championship Tournament 2022, Copenhagen Hnefatafl 11x11, 262 moves, 2022-10-16 19:09:09, black won (Cacreal)

In the first image from left to right the black vikings on D6, E7, E8, D9 and C10 are preventing the white's vikings from reaching the right side of the board as well as the king from escaping to the upper left corner. After couple of moves, the position transformed into another flock formation but this time the blacks used it to protect the upper side of the board isolating the king from his main forces who were ready to build an exit fort. In this game Cacreal really showed how to use the flock formation effectively to stop the white's attacks.