The Church of the East declined in China substantially in the mid-14th century. Several contemporaries, including the papal envoy John of Marignolli, mention the murder of the Latin bishop Richard and six of his companions in 1339 or 1340 by a Muslim mob in Almaliq, the chief city of Tangut, and the forcible conversion of the city's Christians to Islam. The last tombstones in two East Syriac cemeteries discovered in Mongolia around the end of the 19th century date from 1342, and several commemorate deaths during a plague in 1338. In China, the last references to East Syriac and Latin Christians date from the 1350s, and it is likely that all foreign Christians were expelled from China soon after the revolution of 1368, which replaced the Mongol Yuan dynasty with the xenophobic Ming dynasty.