The antonyms for the phrase "base operations" would be words that convey the opposite meaning of operating a base. These might include terms such as "cease operations," "shut down," "disband," "decommission," "abandon," or "vacate." These antonyms imply the cessation of activity, removal of resources, or dismantling of infrastructure in a base, which could occur for a variety of reasons such as budget cuts, withdrawal of troops, or changes in strategy. In contrast to the active management and utilization of resources in base operations, these antonyms suggest a lack of activity or presence, and a return to a state of disuse or abandonment.