Complete the following sentence: "Rasputitsa" seasons of Russia are well known as a great defensive advantage in wartime. ️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️<unk>️ A spring thaw probably saved Novgorod from conquest and sacking during the 13th century<unk>
Mongol Invasion.