Here's how Wikipedia describes it.

The Nakba (Arabic: النَّكْبَة an-Nakba, lit. 'the catastrophe') was the ethnic cleansing^[2] of Palestinians in Mandatory Palestine during the 1948 Palestine war through their violent displacement and dispossession of land, property, and belongings, along with the destruction of their society, culture, identity, political rights, and national aspirations.^[3] The term is also used to describe the ongoing persecution and displacement of Palestinians by Israel.^[4] As a whole, it covers the fracturing of Palestinian society and the long-running rejection of the right of return for Palestinian refugees and their descendants.^[5][6]

During the Nakba in 1948, approximately half of Palestine's predominantly Arab population, or around 750,000 people,^[7] were expelled from their homes or made to flee, at first by Zionist paramilitaries through various violent means, and after the establishment of the State of Israel, by the Israel Defense Forces.

There's just one problem: It's nonsense that eliminates almost all relevant context about what truly happened.

The entire purpose of the above excerpt is to paint the Palestinians as innocent victims of Israeli aggression. Nowhere is there a mention of who started the war, nor is there any indication of why the vast majority of Palestinians left their homes. Instead, the framing is that of violent Jews forcibly removing every Arab they came across as they heartlessly "stole" Palestinian land. The truth is far different and much more nuanced.

The modern Nakba narrative was largely birthed in the 1980s by left-wing historians in an attempt to express their opposition to "Zionism." As with most things Palestinian, nothing about the movement is organic. Even the keffiyeh head covering all the modern pro-Hamas activists wear was created by a British official in the 1950s. The entire concept of being "Palestinian" instead of simply Arab was popularized in the 1960s as a way to project the existence of a distinct demographic worthy of revolution. 

(For an excellent breakdown of how the modern-day Nakba narrative came about as well as some of the historical details I'll be discussing below, click here)

With that said, what is the truth of the supposed Nakba, which means "disaster" in Arabic? Putting aside the absurd contention that the Jews, who were woefully outnumbered in 1948, somehow physically carried out an "ethnic cleansing," we need to start with how the Israeli War of Independence began. 

According to the U.S. State Department, which has hardly been hostile to the Palestinian cause over the preceding decades, the first organized fighting occurred as a result of Arab Liberation Army attacks on the Israeli side of the UN partition. 

Fighting began with attacks by irregular bands of Palestinian Arabs attached to local units of the Arab Liberation Army composed of volunteers from Palestine and neighboring Arab countries. These groups launched their attacks against Jewish cities, settlements, and armed forces.

Why were they attacking Jewish cities and settlements on the Israeli side of the partition, which at the time was a small fraction of the former British mandate, with the Arabs being given almost all of the land, including all of modern-day Jordan? The simple answer is that having previously allied with Adolf Hitler during World War II, they were trying to prevent the creation of a Jewish state for very obvious reasons.

On that note, did the Jews just randomly show up after World War II to claim land given to them by the UN? Certainly, some Holocaust survivors did make their way to what would become Israel, but much of the original Israeli state was composed of land that was legally bought in the early 1900s. For example, Tel Aviv was developed on land that was deemed largely useless at the time. In other words, the Jewish state was set to be formed on a small sliver of land deemed to be of no real value to the Arabs.

That plan was never allowed to come to fruition, though, because the Palestinians and their Arab allies (Lebanon, Syria, Iraq, Egypt, and Saudi Arabia) attacked on May 15th, 1948, the day after Israel declared its independence. Their express intent? To drive the Jewish state into the sea, murdering as many Jews along the way as possible. That's where the genocidal chant "from the river to the sea" originates.

So why did so many Palestinians leave in what is now called the "Nakba?" The answer is that the Grand Mufti, the Palestinian leader in exile who had allied with Hitler, ordered them to. At the time, it was thought that an Arab victory was imminent given how outnumbered and outgunned the Israelis were. Palestinians voluntarily left in droves with the expectation that they'd be able to return after a glorious victory.

Further, the Israelis told the Palestinians that they could remain in their homes if they laid down their arms. The Grand Mufti rejected that offer and ordered the war to move forward.

Stone blames the grand mufti for giving explicit orders to the Palestinians to abandon Haifa, which had the largest Arab community of any city assigned to the Jewish state under the UN’s partition plan.

(...)

In describing the battle for Jaffa, the Arab city adjoining Tel Aviv, Karsh uses British military archives to show that the Israelis again promised the Arabs that they could stay if they laid down their arms. But the mufti’s orders again forbade it. In retrospect, it is clear that the mufti wanted the Arabs of Haifa and Jaffa to leave because he feared not that they would be in danger but that their remaining would provide greater legitimacy to the fledgling Jewish state.

This is where the entire Nakba narrative demands far more nuance than is ever afforded by its proponents. Did Israel expel some Palestinians during the fighting in cities like Lydia? The answer is yes. Some were sent on the road to the West Bank as refugees given there was an active war going on.

The question then becomes how Israel should have responded after winning the war, which it ultimately did decisively. There is no historical precedent for a nation that was invaded to immediately welcome back with open arms the very people who tried to exterminate them. Israel did expand its land holdings during the 1948 conflict, but that was a result of the Palestinians and Arabs losing a war they started. 

The expectation at the time was that the Palestinians displaced due to the war they lost would be absorbed into the neighboring Arab states, including the Palestinian-majority state of Jordan. At the same time, Israel was left taking in nearly a million Jews who had been expelled from Muslim nations. That never gets talked about, though, because it doesn't fit the Nakba narrative. 

In short, the entire Nakba narrative is a modern fabrication, penned by liberal "historians" seeking to paint the "Palestinians" as innocent victims of "Zionist" aggression. It completely ignores the chain of events and historical reality of what occurred in 1948 and beyond. 

The fact that "Nakba Day" is on May 15th, the day the Arab alliance declared war on Israel gives the game away. They aren't upset about a supposed "ethnic cleansing" that occurred the day after Israeli independence. They are upset that they got their clocks cleaned and lost territory in the process. Perpetual victimhood omitting their self-destructive actions is the Palestinian way. That's the truth of the Nakba narrative.