In 1812, Napoleon Bonaparte attempted an invasion on Russia. He wanted to end the war in 20 days. But to his surprise, while travelling through Russia, he discovered that the road network was very bad, which took longer than Napoleon thought. Food supplies began to end, so soldiers had to eat whatever they could find on the road, horses began to die, diseases controlled the soldiers. But they kept going deeper and deeper in Russia (Which got of course harder and harder to survive). The weather was a major problem too: It's either too hot and dry, either too cold. Less than the quarter of the soldiers return home: But no Healthy. The invasion was a total catastrophe. Till now, Massive Russia has never been fully conquered.
Hope this Helps! :)