I have to confess that my knowledge of the history of weapons is rudimentary, so I gladly accede to your point; my previous remark only concerned Soviet geopolitics as it stood in 1947 vs. 1920.
And your point was correct, and sloppy of me. I knew that one of the reasons Trotsky split from Stalin was over Socialism in One Country (in addition to the growing bureaucracy), but I'd thought it was still always the plan to eventually spread socialism globally.