This timeline is to illustrate some key points in the history of "Judea on the Danube", as this alternate Hungary was poetically named (its actual name was Yisrael Khadash, "New Israel", but most people typically called the new country Israel).
The timeline's original POD is around 950 CE, as Radhanites, Jewish traders wandering around the Eurasian supercontinent, distract the Khagan during some forgotten battle against the 'Rus. The traders in question are fed information by 'Rus traders and told to take it to the Khagan's army.
The Khagan's generals believe the traders, and they thus commit a fatal blunder that opens up the Khaganate to 'Rus warriors. The Khazar Khaganate falls to the 'Rus about 18 or 19 years early. (The dates are inexact because of poor OTL record-keeping.)
There is an interesting (but dubious) hypothesis out there, called the "Khazar hypothesis", that claims the OTL Khazars were the ancestors of the Ashkenazi Jews. However, genetic research appears to put Ashkenazi ancestry closer to Italy and the Levant than to the southeastern Ukraine, where the Khazar homeland was.
Nonetheless, this Khazar hypothesis is useful for alternate history.
In the OTL 10th century, the Kievan 'Rus state defeated the Khazars, after the Byzantine-Khazar alliance that had been in place collapsed, and the 'Rus converted to Eastern Orthodox Christianity in 986. The Hungarians became Christians sometime around OTL 1000.
- 950 - Fall of Atil, the Khazar capital, to the 'Rus. The Khagan and many of the Khazar elite decide to migrate westwards to the Carpathian basin, following their old allies the Magyars. A few Khazars follow Radhanite traders all the way to where many Jews had already settled, in the cities and towns along the Rhine.
- 973 - Joseph ben Aaron, the former Khazar khagan, wows the leaders of at least six of the eight Magyar tribes at a Magyar tribal council in the Carpathian basin with his speech. (One of the tribes, the Kabar tribe, which had formed out of three tribes that rebelled against an earlier Khazar khagan, is not as enthused, and one leader is somewhat between the two sides.)
- 975 - One of the Magyar leaders converts to Judaism and takes the name of David, King of the Hungarians and Khazars.
- ca. 950-1000 - A wave of Jewish settlers spread into the Rhine, as Vikings, 'Rus, and other troubles make trading across Eurasia somewhat difficult. Also, Jews are migrating from places such as Italy. This occurs in a manner somewhat like OTL, except that the River Danube is a bit more attractive.
- 986 or 988 - As in OTL, Vladimir of the 'Rus converts to Byzantine Rite Christianity. Jews are even less of an influence on Vladimir in TTL because not as many Jews are left in the Ukraine.
- 1053-4 - The Byzantines and Pope excommunicate each other, starting the schism between the Latin and Byzantine Rites, as in OTL. The people practicing the Latin Rite become the Roman Catholic Church, while those practicing the Byzantine Rite becomes the Eastern Orthodox Church. (OTL Hungary was mostly Catholic in those early days, with some Orthodox. TTL "New Israel", as the place is already being nicknamed, is multireligious, with Jews having a pluralty, so the split doesn't affect the Carpathian basin as much as in OTL.)
- ca. 1089 - As in OTL, Byzantine Emperor Alexios I Komnenos and Pope Urban II open discussions on how the schism may be repaired.
- 1095 - Byzantine Emperor Alexios I Komnenos, concerned about a Seljuk Turk advance rather close to this capital, asks the Pope, Urban II, for aid. The Pope agrees and heads back to his homeland, France, to speak at a meeting in Clermont, which also happens in OTL. He impresses the people and nobility of France/Germany to Do Something about the "villainous" and "brutal" Turks who are "raping" the "virtuous" and "chaste" Christian wives of Constantinople. (He also talks about the need for Europeans to come together in a "Peace of God", launching a militarized pilgrimage, and of rewards in heaven to anyone killed in such a campaign, including the remission of sins.)
- 1095-1096 - The Pope takes his show on the road, going all around France to drum up support for his campaign. Many of the people who respond are peasants, often half-drunkards, and there are even some women, monks, and ill people who join the campaign (against the Pope's wishes). (Yup, still OTL.)
- 1096 - Pope Urban II inspires numerous rabble-rousers, including the very charismatic preacher named Peter the Hermit. This guy, in turn, motivates Count Emicho of Flonheim. They preach about the End Times and about the coming takeover of Constantinople. Emicho takes this one step further and says that he, himself, will take over Constantinople and become the Last Emperor of the World. After this, his plans are to unite all Christian armies and "liberate" Jerusalem from the infidel Muslims ("Saracens"). Emicho gathers an army in Speyer, and he and his followers sack Metz, Mayence, Worms, Cologne, and Trier, as well as other cities along the Rhine, forcibly converting Jews or killing them wholesale. (All OTL.)
- Later in 1096 - Emicho and his horde sail down the Rhine and then the Danube, where they run into Atil Khadash and Yerushalayim Khadash, the two central towns of Yisrael Khadash - and, more importantly, a Jewish army that had already gotten word of Emicho's atrocities. Already out of food and money, and in infidel territory, Emicho's ragtag army takes to stealing, robbing, raping, and killing. King Reuven is not pleased, and Emicho's army is slaughtered in battle. Emicho is tied to the stake in the middle of New Atil, where he is stoned as an "Amalekite" (enemy of the Jewish people).
- 1097 - Rhineland Jews, shocked at how their fellow countrymen behaved against them, start packing up and sailing down the Rhine and Danube rivers themselves. Their destination: New Atil and New Jerusalem. Also, New Jerusalem has to repel at least two more wayward bands of Crusaders, who mistake it for the original Jerusalem. (Never mind that the Holy Land is on the OTHER side of the Byzantine Empire and Anatolia....!)
- 1099 - By now, the campaigners of the First Crusade have moved off (and reached the original Jerusalem, where the Crusaders have massacred the inhabitants, as in OTL).
- A rather quiet century for New Israel, secure within the Carpathian basin, and working hard to build relations between themselves and both the Christians and Muslims. The country sees itself as a buffer state, keeping religions apart from one another. Ashkenazi brides marry Khazar men, Hungarian brides take Ashkenazi men, and so on and so forth, until the people are quite thoroughly intermarried. Henceforth, European Jewish genetic signatures are quite different from those in OTL.
- Numerous synagogues, both Rabbinic and Karaite, spring up in New Israel.
- 1180 - New Israel spreads south, conquering Bosnia, Dalmatia, and various nearby territories.
- 1211 - there is no Andrew II, because the society occupying the Carpathian Basin is not Christian. Thus, there is no Golden Bull in 1222 restricting the powers of the king (this is already provided for in an earlier Covenant in TTL, so it's not that big a difference from a historical point of view), no expulsion of the Teutonic Knights from Transylvania to the Black Sea in 1225, and no Hungarian leadership of the Fifth Crusade in 1217. The crusade fails earlier than it does in OTL. King Benjamin II declares neutrality in the conflict between the Ayyubids and Crusaders, expressing the hope that "one day Jerusalem will be back in Jewish hands".
- 1241 - Mongols invade New Israel. Major destruction ensues. King Solomon III, unlike OTL Bela IV, he makes a stand after his initial defeat and deflects the Mongols into the middle of the country. (Bela was chased to the shores of the Adriatic Sea in OTL.) While the Mongols still create havoc and devastation, it is somewhat less than OTL's destruction in the same area, and the Mongols still withdraw in 1242.
- 1243 - King Solomon III, like OTL Bela IV, invites foreigners into the country to build its population back up, and he calls for a bulwark of castles and fortresses to defend against the Mongols should they come rampaging again. The introduction of Christian and Muslim foreigners into "Judea on the Danube" is controversial, but they become accepted, as do pagans and other odd religionists. Tengriism makes a small comeback, a side effect of the Mongol invasion.
- 1286 - New Atil defeats the Mongols when they come back for more. Mission accomplished.