Why don't battlements simply have straight tops?

Battlements do not have straight tops because their crenellated design, featuring alternating high and low sections, provides both defensive and offensive advantages. The raised sections, or merlons, offer cover for defenders while allowing them to fire weapons or observe the surroundings through the gaps, or embrasures. This design also helps to deflect incoming projectiles and provides a psychological deterrent against attackers. Overall, the crenellation enhances the fortification's effectiveness in combat situations.