The phrase "march to the cannon mouth" refers to a dangerous situation, where one is facing imminent danger. Synonyms for this phrase include "walking into the lion's den," "entering the fray," "braving the storm," "going toe-to-toe," and "jumping into the fire." These idioms represent the idea of facing and confronting a challenging and dangerous situation with courage and determination. They all indicate the need for bravery and the willingness to take calculated risks. Whether it is a literal battle or a metaphorical one, having the ability to "march to the cannon mouth" is a valuable trait that facilitates growth, development, and success.