I have a friend who wrote a paper on Shabbtai Tzvi, who lived, I believe, some centuries ago in Turkey. Shabbtai Tzvi was a righteous Jew who claimed to be the Messiah, and the whole scandal with him was that he later converted to Islam, and many of his followers also converted. According to my friend, there is much confusion about Tzvi's intent in his conversion to Islam, which is primarily recorded as his converting to save his life, which most Sages opine is allowed with reference to Islam.
There is a Chassidic (Kabbalistic) concept known as "tzim tzum," which loosely means "withdrawal," and it is explained that when G-d created the world, He had to withdraw His Presence from it just enough so that the creations would be able to exist, i.e., He had to make room for everything because His Presence is all-encompassing. It goes on to explain that G-d left sparks of holy light, called "nitzutzim," trapped within the material confines of this world, and through the observance of the Torah, a Jew can release those sparks of light and expose G-d's Presence here. As my friend's paper goes, Shabbtai Tzvi reasoned that many of these sparks of light had become trapped in Islam, which he reasoned was a low spiritual place, and therefore he lowered himself into this place with the intent to somehow gain access to them and to release them into the midst of the world. His "movement" was definitely a Messianic one, and when he entered the sphere of Islam, "converted," his dedicated followers followed with him. As some sources on ancient communities of Jews indicate, the "Donmeh" Muslims of Turkey, whom are recognized as being separate from the rest of the Muslim population, are said to be the converts to Islam and therefore the Jewish descendants of the followers of Shabbtai Tzvi. Although this is not the point of the essay, it could be said that Shabbtai Tzvi was a false Messiah.
However, Tzvi's stance that Islam holds a special power is not at all unfounded. First of all, many of the internal mechanics of Islam function in starkly similar fashion to that of Judaism, enough to spark the interest of a Jew, or at least to persuade a level of respect for it. The very foundation of the religion of Islam was built on its replacement of Judaism, or what Muslims would explain as actually being the pre-Torah revelation by G-d of true submission through all of the figures in the Tanakh (and Jesus). The Qur'an, delivered in the 7th Century, was the physical presentation of this chain of pure faith. Hence, this process of superseding Judaism began in the 7th Century and was still around some hundreds of years later in the Muslim world, and today. The power of truth contained in the religion of Judaism became diminished after the Roman destruction of the Second Temple and the rise of Christianity, which thrived on that truth as does a vampire on blood. Some six hundred years later the religion of Islam was founded and it too thrived on that life force of truth of Judaism. However, by then, a lot of it had been sucked into Christianity and so Islam had two sources from which (it had) to draw. Christianity and Islam both were able to pull Jews into them due to this presence of monotheistic moralistic truth. The more neatly those two religions could present their fulfillment arguments to Jews, glossing over the scars created by grafting narrative to narrative, the better they were at actually persuading Jews that either Christianity or Islam were the fulfillments of Judaism. Whatever truth led a Jew to either of these religions was truth that existed in Judaism, but due to the invasion-like forces of supersessionist propaganda, Christianity and Islam had done a superb job of associating Torah ideas with Christian or Muslim thought.
For example, Christianity and Islam operated by conforming a theological concept found in Judaism to fit either a Christian or Muslim world view, and a Jew who was ill-equipped to recognize the falsehood of such a construction was at danger of joining the ranks of either of those religions. However, lack of knowledge of the Torah is not the entire culprit in those situations, primarily because we are speaking about the time before the mass secularization of Jews in the 19th Century, when Jews became separated from their Torah. There might have been some type of Middle Ages "version of secularization," but for the most part the knowledge of Torah permeated Jewish society in the same way that the knowledge of the Gospels and the Qur'an permeated those respective societies as well. It is most likely that the diminished position of Jews in society under the more cruel of the Muslim rulers (in this case, although Christian in others) created a powerful incentive for persecuted Jews to escape oppression through joining the ranks of the oppressor religion. If we combine all of these elements; inescapable oppression, separation from the Torah, and Islam's similarity to Judaism, we have a powerful formula causing a Jew to teeter into the ranks of Islam. In these cases, the Jew who converted usually adopted a hatefully resentful attitude towards his previously belonging to the Jewish People, and if he rose to any sort of power, he would use it against the Jews. Further, Christianity and Islam both had a way of being suspicious of Jews who could potentially "Judaize" their religions by introducing Jewish elements into them, and so a Jew who converted usually annihilated his previous identification as a Jew as to avoid this. Perhaps this is to what Shabbtai Tzvi alluded when he said that many of the holy sparks of G-dly light had become trapped in Islam. His "conversion" to Islam after claiming to be the Messiah of the Torah, perhaps with his "reconversion" back to Judaism after some time, was intended to lead "at risk" Jews (virtually all of them) to choose Judaism. His Muslim friends and contacts created while he was a "Muslim" would open Muslims up to the goodness of the Jewish People and maybe to the truth of the Torah, (in essence, Judaization) causing them to rescind hateful policies. This maybe would have even led some Muslims to become Jews, because if the similarities were so apparent, then a Muslim could have converted to Judaism just as a Jew converted to Islam. The overall effect would be to cause Jews to be freed from the self-oppressive shackles of spiritual, emotional, and physical destruction caused by Islam's insurgencies into the Jewish soul and entire way of life and would bring about a Messianic age of religious peace and harmony between Judaism and Islam. The sad truth is that Tzvi's attempts, which seemed to understand the situation with beaming clarity, did not function in the way he desired. This is not to say that it would not have worked, but all of the parts that had to fall into place simply did not or at the right time, and so his "movement" essentially failed.
Today a similar situation has, and is developing with regards to Islam and the world. Physically speaking, Islam is the fastest growing religion in the world (partially because one who converts to Islam faces ostracism and death upon rescinding the decision). Spiritually, violence, fear, and thuggery have always been excellent ways to gain a following, take Hitler for example and how he "inspired" almost the whole of Germany to partake in decades of genocide and war. 9/11 was a "turning point" in the 21st century history of Islam to those who were previously oblivious to it, largely America and partially Europe. The suicide bombing murders of Israel had been taking place for decades, but the disintegration of the Twin Towers was a macroscopic version of down-town Jerusalem's almost routine coffee shop explosion. After the shock clouds cleared, two major camps were formed, those who were wrought with anger, hate, and the desire to retaliate. The feeble ones were so scared off of their foundations that they sought to detract anger and hatred away from the demonic forces responsible for 9/11 by likening the symbols of death itself to good and themselves to evil!
Hence began a dark phase, which perhaps has not yet ended, where the pressure that these currents in Islam created pushed so hard on the psyches of the targeted that the defense of and association with Islam became one way to deflect further attack and to neutralize fear. By "letting Islam in" to one's heart and to one's country, i.e., the defense of Muslim civil rights at any cost, soul terrorism initiated the breakdown process initiated, analagous to a digestive process whereby enzymes (terrorism) break down pieces of food (target societies). The indispicable tragedy in this line of emotion (not thought) is that it only stimulates confidence in the virus-like assassins. This is the way otherwise weak groups dominate and sometimes invade entities hundreds of times their size - an invasion does not need to be physical, it can exist in metaphysical "geography." The appearance of power, not to mention, the degree and eagerness for the targeted to give in, and not to kill back, enliven the invaders.
However, to the meek, feeble, scared, instable, weak, and confused, unflinching resolve in an enemy to the point of the justification and inclusion of all types of murder, is skewed in the mind of the weak as confident nobility. If somehow a person who seems rational is able to justify murder, then perhaps the consciousness' immediate rejection to this logic is actually wrong. The confused target then represses his feelings of the disorientation that would otherwise lead to intellegible moral objection, and he leans on the attacking force for power, sustenance, and confidence, and in this he becomes one of them. In other words, he is dominated and taken over, like a puppet.
This is the general effect of this type of terrorism on the "normal" Gentile. However, the effect on the Jew, precisely the effect which Shabbtai Tzvi sought to counterbalance and neuter, is different, especially a Jew with a spiritual inclination.
Take Yosef Cohen, for example. Cohen was a secular Jew who became Orthodox, such as myself, in his early twenties. As he recalls, he was speaking Online with a Muslim in a chatroom one day, and the discussions led to more discussions. After presenting the Muslim with all types of questions, all of which he says were answered, and eventually reading the Qur'an, Cohen decided that Islam was the truth, became a Muslim, and changed his name to "Yussuf Khattab." He has since changed his entire identity into a Jew- and Israel-hating Muslim, unflinchingly explaining that suicide bombings against Jews on busses is just. He alludes to it only shortly in a
video on Youtube, but family and personal instability were factors in Cohen's life growing up, sad realities that can destroy a person's inner-sense of self.But personal life isn't the only factor here. Becoming an Orthodox Jew is a process that is as powerful as a loaded gun and it must be handled carefully and with wisdom. Being a Jew means rejecting the illusions of this world and the attempt to replace it with a sometimes radically different notion. It is a type of thing that can cause a slightly insecure person to take it to the wrong proportions. However, Judaism's existing in an un-redeemed state, i.e., the lack of Temple, right to Jerusalem, inability to complete all the Mitzvot, having to convince the nations that Israel is ours, etc..., are all things that seem to be fulfilled in Islam. Therefore, a very interesting phenomenon with Islam for a particularly lost yet spiritual Jew (and the Cohanim, the descendants of the priests who served in the Temple, of which Yosef Cohen is one, are known for spiritual prowess), is that they identify the spiritual and religious absolutes that are currently lacking in Judaism in Islam. This is exactly what Shabbtai Tzvi, had he succeeded might have been the Messiah, was trying to prevent with Islam, and Yosef Cohen is exactly one of the types of my fellow Jews whom he was trying to save.