Something of an obscured footnote in history, but no less important, was the Soviet Invasion of Finland beginning in early December of 1939. If anything, it gave the Soviets an idea of just how ill-prepared they were to fight a war especially a Winter War and just how formidable an adversary the Finns were. Subsequently, the Soviet Union suffered a devastating morale blow to their credibility and the Finns gained a healthy respect from the rest of the world. The conflict finally ended in March of 1940 when a treaty was signed.
Here is an early report from December 9th, as broadcast by Teresa Bonney, who was a freelance photo-journalist working in Finland at the time. She gives details of the invasion and the evacuation of U.S. citizens from Finland in wake of the fighting.
An interesting report on a conflict somewhat overlooked during the early stages of World War 2.