The phrase "was in the power of" can be replaced with several synonyms that convey a similar meaning. Some options include "under the control of," "at the mercy of," "subject to," "governed by," and "dominated by." Each of these phrases suggests a sense of vulnerability and dependence on an outside force. They are often used to describe situations where one entity holds more control or authority than others and can exert their will over them. Whether describing individuals, groups, or even entire nations, these synonyms can help convey the power dynamics at play and emphasize the stakes involved in any given situation.