What term describes the action of opposing groups forming an alliance?

The term that describes the action of opposing groups forming an alliance is "coalition." A coalition is a formal agreement between parties or groups that come together to pursue a common goal while still having different or even opposing viewpoints. This collective effort is often strategic and allows the groups to leverage their strengths together, thereby enhancing their influence or effectiveness in achieving specific objectives.

In contexts such as politics or advocacy, coalitions are commonly formed to amplify voices and create a united front, even if the groups involved may not see eye to eye on all issues. By banding together, they can also pool resources, share expertise, and reach a larger audience than they might individually. Understanding the dynamics and functions of coalitions is critical in various fields, including organizational behavior, project management, and community development.