The writing of mantras and copying of Sutras using the Siddhaṃ script is still practiced in Shingon Buddhism in Japan but has died out in other places. It was Kūkai who introduced the Siddham script to Japan when he returned from China in 806, where he studied Sanskrit with Nalanda trained monks including one known as Prajñā. Sutras that were taken to China from India were written in a variety of scripts, but Siddham was one of the most important. By the time Kūkai learned this script the trading and pilgrimage routes overland to India, part of the Silk Road, were closed by the expanding Islamic empire of the Abbasids. Then in the middle of the 9th century, there were a series of purges of "foreign religions" in China. This meant that Japan was cut off from the sources of Siddham texts. In time other scripts, particularly Devanagari replaced it in India, and so Japan was left as the only place where Siddham was preserved, although it was, and is only used for writing mantras and copying sutras.