The phrase "marches up the cannon mouth" is a vivid description of an object or animal advancing towards danger or an obstacle. There are numerous synonyms that can be used to express this concept, such as charging, storming, bulldozing, forcing, pushing, and plowing. These words indicate a movement that involves determination, strength, and resilience. They convey the idea of an entity that is not deterred by obstacles or threats, and that strives to achieve its goal regardless of the challenges that lie ahead. Other synonyms that can be used to describe this action include surging, advancing, and bearing down, all of which emphasize the idea of an unstoppable force.