The history of Estonia forms a part of the history of Europe. Humans settled in the region of Estonia near the end of the last glacial era, beginning from around 8500 BC. Before German crusaders invaded in the early 13th century, proto-Estonians of ancient Estonia worshipped spirits of nature. Starting with the Northern Crusades in the Middle Ages, Estonia became a battleground for centuries where Denmark, Germany, Russia, Sweden and Poland fought their many wars over controlling the important geographical position of the country as a gateway between East and West.