Original sentence: Over the millenia, the inhabitants of what is now known as Russia had had ample opportunity to evaluate the martial skills of various invaders: from the Vikings in the West and from the Tatars and Genghis Khan's Golden Horde from Mongolia in the East
Edited sentence: Over the centuries, the inhabitants of what is now known as Russia had had ample opportunity to evaluate the martial skills of various invaders: from the Vikings in the West and from the Tatars and Genghis Khan's Golden Horde from Mongolia in the East