The phrase "march to the cannon's mouth" is often used to describe the act of bravely or recklessly facing danger or adversity. However, there are several synonyms that can convey similar meanings. One such synonym is "go through the fire," which suggests undergoing a difficult or harrowing experience. Another is "brave the storm," which implies facing and enduring a difficult situation. One could also use "dare the gauntlet" to suggest willingly taking on a challenge or "charge into the fray" to suggest a headfirst approach to danger. Ultimately, there are many ways to express the concept of facing adversity head-on, each with nuanced differences in meaning.