A semi-open position is defined as a position with very few or no locked pawns and typically 1 or 2 pawns may have been traded. This position has characteristics of both the closed and open positions but is different from each of them in a few ways. The three factors that we will cover with this position are the plans possible, the speed with which you need to act, and the pieces that are most effective.
A wide variety of different plans are available in semi-open positions. A larger emphasis is placed on piece movement, but pawn pushes still carry some weight. Pawn pushes can be used to gain space and control key squares, but this should always be used in connection with strengthening our pieces. Having strong diagonals for our bishops, far advanced outposts for our knights, and good control of areas of the board is very important.
In the position to the above, we see that the White d-pawn and Black c-pawn have been exchanged. We are in a Sicilian style position and White’s plan here could be to position his pieces on good squares and attack the d-pawn. This could be done by 1.Rd1, 2.b3, 3.Ba3, 4.Nb5 and Black could have some problems with defending the pawn. White’s pieces would be placed optimally, and he would enjoy a nice advantage if he could carry out that plan.
Speed is slightly more of a factor in semi-open positions due to the extra piece mobility each side has. Going back to the position on the right, White has a good plan in place and a series of moves he can play, but Black can change the position a bit by playing 1…Nc6 and attacking the white Queen. Once White moves his Queen, then Black is able to make his own move and can try to change the position to be in his favor instead. Each side must act with some urgency when choosing their plans and moves in a semi-open position.
There is no one most effective piece in a semi-open position. It all depends on the specific situation on the board. Sometimes the rooks can be most effective if they can control a central open file. Other times, a knight will be terrific if it can get to a far advanced outpost. At other times a bishop will be the best piece if it is on a terrific long diagonal. Looking again at the position on the right, both light square bishops are good, facing off against each other on the long diagonal. White’s rook will be well placed on the d-file and a black rook will be placed well on his c-file. The knights are also able to attack the center effectively too.
Read more about the generalities of the three different types of chess positions by clicking here: “Three Chess Positions: Generalities”.