At 2.30 PM, Red Army stages a border incident to justify the coming invasion of Finland. They fire 7 mortar shells into a field near the village of Mainila on the Karelian Isthmus, half a mile inside Soviet territory. Fortunately, they clear the area beforehand and no one is hurt. Unfortunately, they are observed by Finnish border guards.
At 9 PM in Moscow, Finnish ambassador Yrjo-Koskinen is summoned to the Kremlin to be informed that “Finnish artillery shelled the area, killing 4 Soviet border guards and wounding 7 more”. The Finns are asked to withdraw their forces 20 – 25 km from the border.
This flimsy pretext does not fool international observers. John Colville, Prime Minister Neville Chamberlain’s private secretary, calls it “a technique which does not gain in dignity for being second-hand”, noting the similarity with Hitler's excuse for invading Poland.