On this day in 1939, some artillery shells may or may not have landed on or about the Russian village of Mainila.
What is nearly certain is that if shells did land there, they weren't Finnish shells, as their army didn't actually have any cannon cockers in, you know, range to shell the village in question.
Stalin's propaganda machine instantly whipped up a frenzy of panic, as the poor, tiny, defenseless peace-lovers of the USSR would be forced, forced! against their will to defend themselves against the slavering giant of Finnish aggression.
This played about as well in the court of world opinion as one would expect.
In the subsequent war, the Russians won (but only on points) and gained territorial concessions, mostly involving prime real estate and natural resources, which most folks considered unusual behavior from a "peace-loving people" who were "only trying to defend themselves".