The phrase "march up the cannons mouth" can be interpreted in a few different ways. It often refers to bravery in the face of danger or taking on a difficult challenge without hesitation. Synonyms for this phrase could include "daring," "fearless," "bold," or "courageous." Other related words might include "resolute," "unwavering," and "undaunted." These terms all suggest a level of determination and perseverance that is required to face challenging situations, which is exactly what "marching up the cannons mouth" implies. Whether you are preparing for a difficult task or simply need a boost of confidence, these synonyms are sure to inspire you to take on any challenge with courage and resolve.