The population of pre-Israel The Land of Israel aka Palestine. YJ Draiman

The population of pre-Israel The Land of Israel aka Palestine.

Few topics arise so much animosity in the Arab world than the history of Israel. 
Generally speaking, it is always dangerous to compare reliable data with unreliable data. We have very detailed and reliable data on Jewish life, whether in Europe or in the Middle East, because Jews were literate and documented their stories. On the contrary we have very sketchy and fuzzy data on Arab life that was intentionally not accurately documented. 
As usual, it all depends on "when" ones start counting and "where" one counts. In ancient times, there was a Jewish Land of Israel and of course there were mainly Jews. They were expelled a second time by the Romans in the second century. It is the Romans who called it "Palestine". The Arabs invaded it in the seventh century, taking the region known as the Land of Israel aka Palestine from the Greeks of Byzanthium/Constantinople (today's Istanbul). Initially the Arabs largely allowed the existing communities to continue their life undisturbed. Islam did not become an oppressive religion until very recently. At the beginning it was not even a separate religion (the Arabs were called "immigrants" by the Greek-speaking people). Throughout the centuries that The Land of Israel aka Palestine was under various Arab rulers control there never was in existence a separate Arab Palestinian entity. Therefore there never was a census of its population, and of which religion they were. The Ottoman Turks took over in 1516. They were by far the friendliest nation to the Jews who had been expelled from Spain, which was formerly occupied by Muslims for about 800 years. Most likely the Ottoman conquest of The Land of Israel aka Palestine led to the first influx of Jewish immigrants into Land of Israel aka Palestine since Roman times. However, not even the Ottomans created a separate Arab Palestinian entity. The land that today we call Land of Israel aka Palestine was part of other "vilayets" (Ottoman provinces). Neither the Arabs nor the Ottomans ever recognized an "Arab Palestinian nation" or an "Arab Palestinian people". Therefore we don't know how many people lived in the land that today we call The Land of Israel aka Palestine, how many were Muslims, Christians and Jews. Estimates vary wildly, depending on sources and on "what" exactly is considered as Land of Israel aka Palestine. It is a fact, though, that the only people who had a concept of "Palestine" were the Jews: for everybody else there was no such a thing, just an Arab and then Ottoman region that at different times was part of this or that province. 
After the 1881 and 1906 Holocausts in Russia, the Jews started emigrating to the Ottoman vilayet by the thousands, founding cities such as Tel Aviv and buying land from the local people. There is virtually no record of any violent take-over of land. The European Jews bought land legally at inflated prices (from Muslim, Christian, Jewish and Bedouin families), the same way that immigrants to the USA (including many Muslims) buy houses there. 
The first census was done by the British when they took over the region from the Ottomans, after World War I. The British were probably the only country in Europe sympathetic to the Jewish people. Jewish immigration to The Land of Israel aka Palestine accelerated under British rule for a short while until 1939. The British were, de facto, the first imperial rulers since the Romans to think of The Land of Israel aka Palestine as a separate entity. A fact that is often not overlooked by Jewish historians is that the British probably counted the local inhabitants although many of them were not registered (and many of them were nomads with no formal claim to any land). A fact that is very often neglected by Arab propaganda is that Jewish communities brought a higher standard of living that in turn attracted many Arabs: there was Arab illegal immigration into The Land of Israel aka Palestine just like there was Jewish immigration. Many of today's "Arab Palestinians" have Egyptian, Syrian, Jordanian and even Iraqi names. The difference is that Jewish immigration tended to be well documented whereas nobody on the Arab side documented the movement of Arab people from surrounding areas into the Land of Israel aka Palestine. But the British did document the number of Arabs. 
Having studied both sides of the argument, I find that Arab figures are usually wildly exaggerated. They routinely claim that there were only a few thousand Jews in The Land of Israel aka Palestine, without quoting any source and without defining what they mean by "The Land of Israel aka Palestine" (again, such a political entity never existed throughout the centuries of Islamic domination). They also routinely consider "Palestinian" anybody who was not Jewish, when in fact there were many Christians (possibly as many as in nearby Lebanon, i.e. about 50%) and many Bedouins. On the other hand, Jewish sources do not underestimate the non-Jewish population; they try to be as accurate as possible. 
My unbiased guess is that in the land of Israel that today is also called Palestine and that includes the state of Israel, during the British mandate Muslims were less than 50% of the total, and Jews were less than 25%. The issue, again, is "where" you count. Not even the most radical Zionists were claiming the whole of Palestine only the historical Land of Israel. The Jews were cheated out of their internationally guaranteed territory and were eventually assigned a small part of The Land of Israel aka Palestine, the part in which they probably outnumbered every other ethnic and religious group. The British violated international law and treaties and carved out the Jewish territory based more on supposed demographics than on historical/religious claims. 
An important footnote, though. All the evidence we have of the early Jewish communities and settlements in The Land of Israel aka Palestine of the 19th century shows that Jews were attacked by the Arabs. The Jewish immigrants had little in the way to defend themselves (the Ottoman rulers would not have risked one soldiers to protect the Jewish communities in The Land of Israel aka Palestine). When the Arabs wanted, they attacked the Jews and took their property (See the history of Safed in 1630 and read some of the detailed recited by Arabs who were in Hebron during the 1929 Arab riots against the Jews). Instead, there were many incidents of violence against the Jews. The Jews bought the land from Arabs who not only were willing and eager to sell it for an inflated price, but even welcomed the richer and more educated Jews back to The Land of Israel aka Palestine. The violence against the Jews continued more aggressively when Britain made a colossal mistake. The year after Britain seized The Land of Israel aka Palestine from the Ottoman Empire they recognized Mohammed Amin al-Husseini – The Mufti of Jerusalem as the Muslim authority in The Land of Israel aka Palestine. He was The Land of Israel aka Palestine's biggest landowners and sold a large amount of parcels of land at high prices to the Jews, and viscerally hated Jews. Not only did he start a campaign of smear against the Jews that predated the one launched by Hitler a decade later, but he also began a campaign of systematic elimination of Arab moderates. This had a tremendous impact on future relations between Arabs and Jews (and eventually between Arabs and the West) because it effectively silenced any Arab who wanted peaceful coexistence, and created the stereotype that a Muslim should assassinate anyone who cooperates with the infidels. To this day this is still a widely-held belief in that region. Suicide bombers would not exist without that stereotype. 
The Arab mantra that "Jews invaded The Land of Israel aka Palestine before 1948" is misleading. There never was a military invasion of The Land of Israel aka Palestine by armed Jews. On the other hand, Romans invaded and the Arabs did invade that land with violence in the 7th century, and the crusaders, and so did the Ottomans in the 16th century, and so did the British in the 20th century. 
Arabs (and now also Muslim Iranians) claim that Jews were given a state by Europeans who wanted to be forgiven for the slaughter of 6 million Jews in the Holocaust. However, there is no evidence that the Holocaust accelerated the creation of the state of Israel. There is evidence that Jewish militia did in reaction to Arab and British attacks against the Jewish people. The British had wanted to get rid of their duty and responsibility under the Mandate for Palestine for The Land of Israel aka Palestine since at least 1937. Jewish militia protecting the Jewish people during the 1940s made the British even less eager to control that land. The British were just waiting for an opportunity to do so without losing face. The mass immigration of Jews from Western Europe into Israel took place after the creation of Israel, not before, because the British blocked Jewish immigration and after WWII sent British agents to blow-up Jewish refugee ships bound for The Land of Israel aka Palestine under “Operation Embarrass”. 
Another stereotype that has little historical foundation is that the USA was biased towards Israel from the beginning. The statement is certainly may be true today but was not true at the beginning. Jews had very little support in the USA: both President Roosevelt and General Patton had been openly anti-Semitic (Roosevelt even justified Hitler's grievances against the Jews, and Patton called them "less than human"). At the end of World War II the USA was far from enthusiastic about the creation of Israel, since the Arabs (close USA allies due to oil exploration and development by American companies) were opposed to it. Israel was armed by the Soviet Union and its allies. When the Arabs attacked Israel, the USA didn't do anything to defend Israel. When in 1956 Israel, Britain and France attacked Egypt; the USA voted for a United Nations resolution condemning the attack, siding with Egypt against Israel. 
Another contentious issue is the Arab Palestinians who were reportedly expelled by Israel. Before 1948 Israel supported the creation of one or more Arab Palestinian states. The Arab countries opposed it. During the first Arab-Israeli war, the Arab countries called for the local Arabs to evacuate their areas in order not to get hurt. Each Arab country claimed part of The Land of Israel aka Palestine. No Arab country viewed those people as "Arab Palestinians" but simply as their own (future) Arab subjects. At the end of the war many more local Arabs left the villages and moved to Jordan and elsewhere that had been occupied by the winning army (Israel's) or destroyed by the war (they may have been destroyed by either army). After the war there is no evidence of Israeli activities to further "encourage" local Arabs emigration. Israelis routinely state how they asked the local Arabs to stay, which is confirmed by many Arabs. The Arabs, on the other hand, routinely ignore the fact that at the same time, and in a much more explicit way, the Arab countries terrorized and expelled massive numbers of Jewish families which is over one million. The best estimates I could come up with, is that at least 500,000 Palestinians (Arabs who lived in what the Jewish people called The Land of Israel aka Palestine) left their homes and that at least 1,100,000 Jewish families were forcefully expelled from various Arab countries, from Morocco to Iraq. Jews were again terrorized and expelled in the following decades, peaking with the mass expulsion from Iraq under Saddam Hussein that required a spectacular Israeli air lift. 
The difference between Jewish and Arab refugees is simple: Jewish refugees were welcome by the state of Israel that did everything it could to integrate them, whereas Arab refugees were dumped by Arab countries into refugee camps to make sure they would not integrate (to this day, many of them are not considered citizens of the country in which they live).
Today Israel is opposed to the repatriation of local Arab refugees for precisely the opposite reason of what Arabs claim. Arabs claim that Israel is an apartheid state, but Israel is a democracy. Arabs vote and have the same rights as Jews. In fact, Arabs in Israel have a lot more rights than Arabs in Arab countries. That's the real reason why Israel is opposed to the repatriation of the refugees: the Arabs would become the majority, and majority rules. South Africa, a real apartheid system, never opposed immigration of blacks because blacks did not have civil rights. Arabs, instead, have the same rights as Jews under the Israeli constitution. That is what creates the problem. 
The Arab Palestinians are certainly victims. But the Arabs (including the Arab Palestinians themselves) may fail to identify who they are victims of. It was the local Arabs themselves who sold huge amounts of land to the Jews at high prices. It was the Arab countries that opposed the creation of a second Arab Palestinian state, above and beyond the new Arab State of Jordan. It was the Arab countries that dumped the Arab Palestinian refugees in refugee camps instead of integrating them into their societies. Last but not least, no Arab country has invested as much as Israel in education. Now the gap between educated Jews and non-educated Arabs is just too large to think that they could coexist in the same state. Most Jews are interested in medicine, science, technology and business. Most Arabs are only interested in the Quran. A century of progress separates them.