"Another knowledge-transfer from India was iron technology, in use since the 2nd millennium BC in India. Hittites brought it west and when they collapsed, the secrets were widely diffused, not in a 300-year Dark Age, but relatively quickly. The corrosion resistant six-ton, seven-metre high Delhi iron pillar from around 400 and the less well-known pillars in Kollur and Dhar were due to a deliberately high level of phosphorous, demonstrating ancient skills of Indian iron smiths. The technique was by then well-known. Persian King Artaxerxes II (404–358 BC) had a pair of ‘supernatural’ Indian swords that resisted the effects of drenching monsoon weather. Indians had been working with iron when the Delhi pillar was made for about the same time as the west has been using iron until now!"