The phrase "South Pacific Mandate" refers to the territories governed by Japan in the aftermath of World War I. However, there are a variety of synonyms that can be used to describe these territories. For example, they may be referred to as "occupied territories" or "colonies." Additionally, one could use the term "Japan-controlled territories" or "Japanese-occupied islands." Other potential synonyms might include "South Pacific conquests" or "Pacific annexations." Ultimately, the precise terminology used will vary based on the context in which it is being used and the intended audience, but there are a number of ways to describe these territories that would be broadly understood.