David Mamet writes that there are two kinds of places in the world: places where Jews cannot go, and places where Jews cannot stay.
So how exactly have the Jews survived?
According Maristella Botticini and Zvi Eckstein, authors of The Chosen Few: How Education Shaped Jewish History, 70-1492 (Princeton University Press, 2012), the answer has as much to do with economics as with spirituality.
Five major events rocked the Jewish world during those 1,422 years: the destruction of the Second Temple, the rise of Christianity; the birth of Islam; birth of modern Christian Europe; and the Mongol invasion. Since Jews who aren't university professors (and there are some) often view events through a lens of "Is this good or bad for the Jews?" I'll summarize the authors' findings in that manner.
Destruction of the Temple and the rise of Christianity--bad for the Jews. After the year 70, the priests who ran the Temple were no longer in the ascendency, yielding power to the Jewish rabbis and scholars who ultimately wrote the Talmud over the next few centuries. Most Jews (and most of everyone else) were farmers back then. After the destruction of the Temple, the worldwide Jewish population dwindled not just because of war and massacre, but because of economics.
If you were devout and wealthy, you were likely to pay for your sons' Jewish education.
If you were spiritual but didn't have much money, you became a Christian or joined one of the other popular groups that didn't require an expensive Jewish education. What good is a son who can read the Torah if you just want him to help harvest pomegranates? So economics dictated who stayed and who strayed.
The rise of the Islamic empire: surprisingly, good for the Jews.
When Muhammad appeared in the seventh century, Jews began to move from farms into new Moslem-built cities including Baghdad and Damascus. There they went into trades that proved far more lucrative than farming, most notably international trade and money lending. In those arenas, Jews had enormous advantages: universal literacy; a common language and religious culture; and the ability to have contracts enforced, even from a distance of thousands of miles.
The Moslem world then stretched from the Spain and Portugal to halfway across Asia. Anywhere in the Arab ambit, Jews could move, trade, or relocate freely and benefit from their extensive religious and family networks. According to thousand-year-old documents found in the Cairo Genizah, business documents linking Jewish traders across the Arab world would have Jewish court decisions written on the back. So Jews could send money or goods thousands of miles, certain their investments would be safe.
European Christianity from the year 1,000: not so good for the Jews.
If Islamic culture offered Jews a warm welcome, Western Europe was a mixed blessing.
Seemingly every few dozen miles in Western Europe, a different prince or king was in charge, with different laws, different requirements for citizenship, and different attitudes about the Jews. Some places were extremely welcoming of Jews; others less so. Monarchs might boot out their Jewish populations in hard economic times, so that Gentile citizens wouldn't have to repay their loans, only to welcome them back when the economy improved.
Contrary to common belief, Botticini and Eckstein write, Jews weren't forced into money lending because they were forced out of guilds. Under Muslim and Christian rule alike, Jews went into finance centuries before the guilds were even founded. In other words, Jews chose careers in finance the same way the best and the brightest in modern American culture head for Wall Street and business school.
Western Europe, therefore, was a mixed blessing for the Jews. On the upside, they could do business, live their Jewish lives, and establish some of the finest Talmudic academies in Jewish history. Alas, Jews were also subject to massacres and expulsions, which happened with terrifying regularity across the centuries, culminating in the Spanish Inquisition of 1492.
Meanwhile, back in the Middle East: the thirteenth-century Mongol invasion: bad for the Jews. Oh, really, really bad for the Jews.
The relative freedom and safety the Jews enjoyed under Muslim rule came to an abrupt halt in the early 13th century, when Genghis Khan and his marauders attacked and leveled most of urban civilization that the Moslems had so painstakingly built up over the centuries.
With the destruction of cities and urban institutions, those Jews fortunate enough to survive the Mongol invasion had no option other than going back to farming. Some stayed; some converted to Islam. So the numbers of Jews in formerly Arab lands would remain low for hundreds of years, until all traces of Mongol civilization were wiped out and the world began to rebuild.
The poet Ogden Nash once wrote, "How odd of God/To choose the Jews." If you've ever wondered how the Chosen People survived the vagaries of history, reading The Chosen Few will give you answers you cannot find anywhere else.