This was said to be largely due to the Battle of Khalkhin Gol that caused Japan not to join forces with the Germany against the Soviet Union, even though Japan and Germany were part of the Tripartite Pact.
Even though Japan and Germany were part of the Tripartite Pact. This was what this was said to be largely due to the Battle of Khalkhin Gol that caused Japan not to join forces with the Germany against the Soviet Union.