"Put up one's dukes" is a phrase typically used to mean raising one's fists in preparation for a fight or to defend oneself. There are a variety of synonyms that could be used in place of this phrase depending on the context. Some examples include "raise one's fists", "assume a defensive stance", "get ready to brawl", or "square up". Each of these phrases conveys the same basic idea of preparing to fight or defend oneself, but may be better suited to different situations or styles of speech. Therefore, it's important to choose the appropriate synonym for the specific context.
