Mashhad's rulerTemplate:Clarify me had ordered his men to enter Jewish homes and mobs attacked the Jewish Community, burning down the synagogue, looting homes, abducting girls, and killing between 30 and 40 people. With knives held to their throats, the Jewish patriarchs were forced to vocally proclaim their "allegiance" to Islam as it was agreed upon by the leaders of the community that in order to save the remaining 2,400 Jews, everyone must convert. Most converted and stayed in Mashhad, taking on Muslim names, while some left for other Iranian Jewish communities and to Afghanistan. That day became known as the Allahdad ("God’s Justice") and the Jews perceived it as a punishment for their sins.
The Jews who remained in Mashhad then began living a double life as crypto-Jews. On the outside, they acted as Muslims: their clothes, names, and lifestyles resembled those of their Iranian neighbors. At home, however, they secretly taught their children to read Hebrew, lit candles, and observed Shabbat.
Nearly a century passed before Mashad's Jews started practicing their faith openly with the coming of the more liberal Pahlavi dynasty (1925–1979). After World War II, most of them settled in Teheran or in Israel, with 4000 moving to the United States, where many ran successful jewelry and carpet businesses. The commercial district in Great Neck, New York, has been reshaped to serve the needs of Mashhadis and other Iranian Jews. Many businesses there cater to Iranian customs and taste.
Worldwide there are 15,000 Mashhadis, of which about 10,000 live in Israel. Of the Mashhadies in the United States, many of the young generation study in Haredi Yeshivas. The more observant group has formed its own congregation, Shira Chadasha. The Mashhadis are susceptible to genetic disorders because of the high rate of in-marriage in their tightly-knit community.