The phrase "march to cannons mouth" refers to boldly advancing towards a dangerous situation despite the risks involved. Some synonyms of this phrase are "head straight into danger" or "walk into the lion's den". Another phrase with similar meaning is "play with fire", indicating recklessness and potential danger. "Courting disaster" and "tempting fate" are also synonyms for this phrase, both suggesting a disregard for potential consequences. Overall, these synonyms emphasize the notion of pushing forward despite the dangers, showing bravery and fearlessness in the face of adversity.