As soon as you change the chessboard in chess, you have to re-assess the relative value of the pieces, as a piece's value is directly affected by its mobility and scope. Note that this is already the case in game on the conventional 8-by-8 boards since how much activity our pieces can benefit from depends on how much space we control, which itself depends on the pawn structure, etc. So in any game, the relative values are changing constantly based on the configuration of the pieces. Thus, to answer your question about finding viable strategies, we first have to develop a good feel for how the values of our pieces are being affected when placing them on a longer board.
What we seem to have is an
l-by-8 chessboard where
l denotes the length of the elongated side (units being a square's side, or simply the count of squares). Since we've only scaled one dimension of the board, here the vertical one, then only pieces that move vertically (or generally laterally) can benefit from the scaling of the board, as they gain mobility (number of legal moves available to them) proportionally to
l. The only pieces that satisfy this kind of movement are the queen and the rooks, so clearly:
- Rooks and queens are the most important pieces here and have a higher relative value to the other pieces (for
l>8) w.r.t the known relative values on a
So in short, the scope of our queens and rooks become greater on the longer board and whatever strategy we adopt, should emphasise the activity (and protection) of these pieces, specially early on if we are to achieve any small advantage.
Now let's see how much the other pieces are affected:
Bishops: since we don't scale the board in both dimensions (and thus not changing the long diagonals), bishops's scope remains roughly the same. For example, when centralised they will have at most 14 legal moves on an empty board, while they have 13 on the
8-by-8. Moreover, they will have to go through a long zigzag across the board until they see the opponent's pieces (so they cost many tempi). Most importantly, we no longer have long diagonals that span the board, i.e., bishop fiachetti are much less meaningful now since they cannot eye the opponent's kingside or queenside, let alone taking away squares from their camp. So bishops, despite being still fast pieces, seem to be less effective on a longer board.
Knights: Knights as always are rather very slow pieces, and here it's the same. So naturally, for their activation they will cost us even more tempi that the bishops. Moreover, their scope is not affected by the scaling of the board (it would if
l<8). So everything being the same, just placed on a longer board, will render knights into even slower pieces, thus their relative value suffers as well w.r.t the
8-by-8 case. Lastly, knights are particularly good when they can be estalished centrally and on permanent outposts: i.e. a square that is well covered by our own pawns but impossible to attack by our opponent's respective pawns. However, since the longer board means the pawns take
l times longer to advance to anywhere near our opponent's camp, we will not be able to create meaningful outposts for our knights anytime soon. So, early on specially, knights seem to be rather useless.
Pawns: as already hinted at in the previous point, pawns will be ever slower the longer the board is. This means for a good chunk of the early game, we cannot secure any valuable space with our pawns. More importantly, there are no pawn moves that take away squares (and thus options) from our opponent's camp at the beginning, which makes a strong case for the fact that on an
l-by-8 board with
l much larger than
8, white's extra tempo becomes negligible and the game is already equal from the get-go. For the contrasting case of
8-by-8 see e.g. the discussions here.
Kings: King safety becomes funny to judge now, on the one hand, one can argue the king is even safer on the
l-by-8 since our opponent's pieces are so far away which makes it very difficult for any threats to be made, which gives us lots of tempi to re-arrange our pieces however we want. On the other hand, if we are to start a long journey with our pieces to eventually reach the opponent's side, our king might be left stranded far away from our coverage and thus rather exposed (e.g. as soon as bishops, rooks and queens can sneak through the structure to reach our king). And if all this means that we need to collectively move our pieces towards the enemy, so they can constantly eye one another, then our advancement speed is bottlenecked by that of the king's... What is roughly the same, is the fact that the board still has edges, so castling our king so it can be tucked away to a corner and only accessible from one side is still possible, but how much of protection that offers, is hard to judge.
Rooks and queens: We have already covered those in the starting discussions.
So in a nutshell, our reassessment of the pieces is:
- Rooks and queens are made even stronger relative to the other pieces.
- Knights and pawns are made weaker since their mobility is not affected and they have only become slower (since it takes longer for them to cross the board and reach the opponent's side).
- Bishops are neither here nor there: their scope is roughly the same (e.g. in terms of legal moves) but they are still quite fast pieces, and with a few zigzags they can cross the board and create threats or coordinate eventually with our heavy pieces. So they remain strong, but less than their worth on an
8-by-8 board since there are no long diagonals spanning the board. But clearly among minor pieces, they are definitely much stronger than knights on the elongated board.
Two basic strategies to consider:
Now that we have a better idea for how the relative value of our pieces is being affected by elongating the board, we have a better chance of finding good strategies. The obvious things that come to mind:
Use your early tempi to quickly activate your queen and rooks in order to already pose threats to your opponent, e.g. by being the first in having an active rook, you will be the first to slow down the advance of your opponent's pawns, and that ought to be your first easy way of gaining a small plus.
Once your heavy pieces activated, I see two separate options: (1) creating a small squad and moving that towards the opponent's side or (2) moving collectively all of our pieces across the board, which is safer since our king is less likely to become stranded compared to (1).
Let's delve bit deeper into each:
In (1): say your two bishops, the two rooks and the queen, that's a 5 piece squad that can coordinate an attack against your opponent rather quickly, either to win material, or to try and bait tension on one side, and sneak through on the other side with a heavy piece. Infiltrating behind your opponent's pieces and winning potentially lots of material, this is more the middle game since we're assuming our opponent's pieces are somewhat close to the center of the board. Admittedly, this strategy resembles more what typically occurs in the strategy game Stratego, where pieces have well-defined ranks which acts as their strength (a lower rank cannot capture a higher one etc), and thus, one typical strategy is to infiltrate our opponent's camp with a small squad of high ranked pieces and mop up their pieces (assuming we know where the bombs are...).
In (2): ultimately, once the gap in space between our pieces and our opponent's have become smaller, the gameplay will approach that of the conventional chess on an
8-by-8 board, and thus we can adopt our usual mindset and conventional strategies become viable again, which means we'll have a more normal game than in (1).