Historical Soviet interest in attending rose when German participation seemed possible, before France and the United States quickly quashed the rumor. A longer-lived rumor, or a quicker reaction from Stalin, provides a smaller divergence than inventing a new merchant empire or global naval need. Moscow could send its naval chief of staff alongside a senior diplomat such as Maxim Litvinov or Vyacheslav Molotov. Their purpose would be to prevent a German advantage and gain influence over the rules. Stalin's priority remained Soviet security rather than international prestige for its own sake.
Chapter · 25:48-33:42
A German invitation rumor brings Moscow to London
The most plausible trigger for Soviet attendance is a longer-lived rumor that Germany might join the 1930 conference.