The spelling of the phrase "marched up cannon mouth" can be a bit tricky. Let's break it down using IPA phonetic transcription. "Marched" is spelled /mɑrtʃt/, with the "ch" sound pronounced like a "tsh." "Up" is spelled /ʌp/, with the "u" sounding like the "u" in "cup." "Cannon" is spelled /ˈkænən/, with the stress on the first syllable and the "n" pronounced twice. "Mouth" is spelled /maʊθ/, with the "ou" sounding like the "ow" in "cow." Together, this phrase describes the act of marching up to the mouth of a cannon.