How effective was the League of Nations in halting Japanese imperialism? They called on all member nations to fight the Japanese. They asked the US to join the League to replace Japan. They condemned the Japanese but couldn't do anything to stop them.

The League of Nations was ineffective in halting Japanese imperialism. While they condemned Japanese actions and called on member nations to oppose them, the League lacked the means to enforce its decisions. The request for the U.S. to replace Japan was unsuccessful, and the League ultimately failed to prevent Japanese expansion in the lead-up to World War II.