What problem did bastions solve at the base of fortress walls?

In the context of military science, the primary problem that bastions solved at the base of fortress walls was the existence of "dead space"—an area immediately below the parapet or along the wall's footing that could not be targeted by defenders.12

Before the adoption of polygonal bastions, circular towers and straight walls often left blind spots where attackers could safely approach to undermine the masonry or use battering rams without being hit by defensive fire. By incorporating a projecting design consisting of two flanks and two faces, the bastion allowed defenders to provide flanking fire that swept the face of adjacent bastions and the curtain wall connecting them. This eliminated the unprotected footing at the base of the wall, ensuring there were no gaps in the defensive field of fire. Additionally, the straight sections of polygonal bastions provided more space to mount larger artillery batteries compared to older, rounded tower designs.321