Four centuries ago there was an incident that can serve as an example of the power of fear. It was the occasion of the last Tatar invasion of Russia in the fall of 1462. The two armies faced each other on the banks of the Oka River, which is located about 200 miles east of Moscow. For several days they had been engaged in battle. When the Tatar army would attempt to cross the Oka River, they would be beaten back by the Russians. It was the Oka River that gave the inferior Russian army any chance of surviving. After several days it began to appear that the river would be all the Russians needed to be saved from the onslaught of the Tatars. But then something happened that frightened them greatly. A cold wave developed that blew down the Ural Mountains and caused the Oka Rive…