Japan was plenty concerned, especially remembering the last time they met USSR military. [2]
In fact, memories of that smashing were arguably the reason Japan turned east to Pearl Harbour, rather than west to Soviet Union. [3]
[1] https://www.warhistoryonline.com/instant-articles/red-army-i...
[2] https://en.wikipedia.org/wiki/Battles_of_Khalkhin_Gol
[3] https://www.goodreads.com/book/show/13102802-nomonhan-1939