For instance, in one variation, it is White who delays pushing their rook pawn (whereas Black delays the rook pawn push in the modern era) and an early bishop trade occurs before both players' kings are moved into their castles.
Rapid Attack Fortress strategies are characterized by the fact that White will start the fight following Black's blocking of the bishop's diagonal.
These are active plans where White wants to avoid a development in which Black takes hold of the initiative.
The side playing Fortress aims at building up a position wary of the rival's rapid attack.
There are a number of variations: The rapid attack strategy will vary depending on whether in the fifth move Sente plays P-66 or S-77.