When Israel won its independence in 1948, a massive number of Palestinian refugees was created as a result. Though estimates vary, about 85% of the Arab population (around 800,000 people) of what became Israel either fled the fighting or were forcibly expelled. When the war ended in Israeli victory, the United Nations passed a non-binding resolution calling for Israel to allow “refugees wishing to return to their homes and live at peace with their neighbors” to return. But Israel did not permit any refugees to return.

Palestinian refugees largely found shelter in refugee camps in the West Bank, Gaza, Lebanon, and Syria. Some eventually found themselves in other Middle Eastern, European and Western Hemisphere countries. Many refugees continue to live in camps. In some countries, they have acquired citizenship, but most refugees in Arab countries, as well as those in the West Bank and Gaza Strip, are not citizens of any country. Over the past 67 years, the Palestinian refugee population has grown to over 5 million people.

Israelis see the Palestinian refugees as a major threat. Whether they see any merit to the claims of Palestinian refugees or not, they fear that if they allow any ground on the Palestinians’ claim to the Right of Return (to their homes and home country), the Jewish majority in Israel will quickly disappear. Israeli Jews do not wish to be a minority in the one country where Jews have been the majority.

But for Palestinians, there is no more important issue. The humanitarian dimensions alone are great. About 1.4 million refugees still live in the camps, in conditions that are often overcrowded and impoverished. Even in places where Palestinian refugees are not in camps, they are often barred from full participation in the society around them, and frequently face discrimination.

But beyond the humanitarian concerns, the refugee issue has become a cornerstone of Palestinian nationalism. Many Palestinian refugees still have the keys and deeds to houses that no longer exist, but they keep them as symbols of their desire to return to Palestine, a land they still have a fierce attachment to.

If Jerusalem is the most volatile issue between Israelis and Palestinians, the refugee issue is the one on which they are farthest apart. One would have a much easier time finding Israelis who are willing to share Jerusalem than those who are willing to admit the Palestinians have any “right to return.” For their part, while polls have shown that many Palestinians would not want to return to what is now Israel, almost all Palestinians believe the choice between return, compensation, or resettlement must be decided by each individual refugee.

Terms of negotiations between Israel and the Palestinians over the years have generally concluded that Palestinian refugees would be given the choice between returning to the proposed Palestinian state, and receiving compensation and being resettled in third countries. Outside of a token number of refugees, the choice to return to their former or ancestral homes in Israel would not be available. These discussions were largely held without the input or knowledge of most Palestinians. When news broke in 2011 about the terms in which the refugee issue was being discussed, the Palestinian public was outraged. It was a major factor in the decline of Palestinian President Mahmoud Abbas’ support.

The international community has largely remained silent on the refugee issue. Since the 1949 UN resolution, the “refugee problem” has mostly been addressed in vague terms of finding an “equitable solution” which could be agreed to in negotiations. That, by definition, means a solution Israel could accept, and that means no significant return of refugees to Israel. It remains to be seen what the Palestinian reaction to such an agreement would be, but polls routinely indicate it would be overwhelmingly negative. These positions leave little room to find a negotiated settlement that would be acceptable, even if grudgingly, to both parties.

For Israelis, no other issue threatens their identity nearly as much as the refugees. Denial of the Right of Return, they believe, is crucial if Israeli Jews are to avoid becoming a distinct minority in what is now Israel. More than that, the very existence of the refugees raises uncomfortable questions about Israel’s history, particularly its birth. Thus, an issue which is at the very heart of Palestinian nationalism is also seen as absolutely central to Israeli-Jewish national existence, making the refugees the most difficult issue on which to find a sustainable compromise.