It was during the Ming Dynasty (1368-1644) that the Wall took on its present form. Each Dynasty added to the heighth breradth and length and watch towers and modern cannon were added at strategic points. The wall served well until the Mongols and Manchurians took advantage of an interior rebellion and were able to take over the weak government and its impoverished people. The Great Wall stretches over 4,000 miles and it was reported that 2 to 3 million Chinese died during the 200 years of construction.