“Immediately after the partition plan, Jewish terrorist organizations attacked innocent Palestinians with the aim of carrying out ethnic cleansing”
A month before the passing of the UN Resolution, Israel Galili, the Hagana’s Chief of staff estimated that:
“As far as we know, it is the Mufti’s belief that there is no better way to ‘start things off than by means of tenor, isolated bombs thrown into crowds leaving movie theatres on Saturday nights. That will start the ball rolling. For no doubt the Jews will react, and as a reaction to a reaction there will be outbreak in another place … [until] the whole country will be stirred up, trouble will be incited, and the neighbouring Arab countries will be compelled to start a ‘holy war’ to assist the Palestinian Arabs.”
To prevent this scenario from becoming a self-fulfilling prophecy, the Hagana’s initial response to the outbreak of violence was essentially defensive, trying to strike a delicate balance between the need to create a credible deterrence and the desire to prevent the cycle of violence from spiralling to uncontrollable peaks. It was only on 9 December, as Arab attacks on Jewish transportation across the country began to have a palpable effect, that the Hagana’s head of operations, Yigael Yadin, ordered commanders to respond in kind so as to curtail the Arab campaign against Jewish transportation 
Lehi was caught unprepared when Britain announced its intention to withdraw and the United Nations approved the Partition of Palestine — both spiritually and practically. Lehi had no prepared plan because its members could not believe that the British would keep their word. Lehi still supported the “neutralization of the Middle East” philosophy, which saw all peoples seeking liberation as natural allies, including the Arabs. This is why Lehi did not respond to the Arab riots in Decemebr 1947, demanding only that order be restored. It even suggested to the Haganah that the combat division of Lehi was at its disposal. The Lehi central committee still believed that there would not be a Jewish-Arab war.
The lehi published Arabic-language pamphlets calling for peace, brotherhood, and a shared struggle against the imperialists victimizing both populations and forcing them into needless conflict. they believed that the Jewish-Arab fighting that had broken out following the publication of the UN partition plan would not escalate but would subside once the British fully withdrew from the country. they hadn’t counted on the British inciting and leading an invasion of neighboring Arab armies into Palestine following their withdrawal. 
The Irgun also began carrying out reprisal missions. At the same time though, it published announcements calling on the Arabs to lay down their weapons and maintain a ceasefire:
“The National Military Organization has warned you, if the murderous attacks on Jewish civilians shall continue, its soldiers will penetrate your centers of activity and plague you. You have not heeded the warning. You continued to harm our brothers and murder them in wild cruelty. Therefore soldiers of the National Military Organization will go on the attack, as we have warned you…. However even in these frenzied times, when Arab and Jewish blood is spilled at the British enslaver, we hereby call upon you … to stop the attacks and create peace between us. We do not want a war with you. We are certain that neither do you want a war with us…” 
The confrontation actually started when the Arab Higher Committee proclaimed a three-day nationwide strike to begin the following day. It enforced the closure of all Arab shops, schools and places of business and organised and incited large Arab crowds to take to the streets to attack Jewish targets. The main such attack took place in Jerusalem on Tuesday 2 December, when a crowd of several hundred Arabs ransacked the new Jewish commercial centre, lying opposite the Old City’s walls, looting and burning shops and stabbing and stoning whoever they happened upon. A Hagana platoon that was rushed to the area to protect civilians was peremptorily stopped and disarmed by the British police, with 16 of its members arrested for illegal possession of weapons. Some of the confiscated weapons were later found on killed and captured Arab rioters. From the commercial centre, the mob proceeded to the City Hall, where they attempted to lynch several Jewish municipal workers and to plunder nearby stores. ‘For a long time the police did not interfere with this little mob,’ recollected the city’s British mayor, Richard Graves, ‘and it was heartbreaking to see these young hooligans being given a free hand to destroy the products of man’s labours … I remonstrated with the police [who] told me that they had orders not to interfere till they were reinforced.’ On 4 December, some 120–150 armed Arabs attacked kibbutz Efal, on the outskirts of Tel-Aviv, in the first large-scale attempt to storm a Jewish settlement. Four days later a more audacious assault was launched when hundreds of armed Arabs attacked the Hatikva quarter in south Tel-Aviv.
“Plan Dalet was an ethnic cleansing master plan”
This is a myth I have already refuted in a previous article “There was no Zionist ethnic cleansing plan in 1948”
But here to add more context.
From January onward, Arab operations became increasingly militarized, with the intervention of a number of regiments of the Arab Liberation Army (consisting of volunteers from Arab countries) inside Palestine, each active in a variety of distinct sectors around the different coastal towns. They consolidated their presence in Galilee and Samaria. Abd al-Qadir al-Husayni came from Egypt with several hundred men of the Army of the Holy War. Having recruited a few thousand volunteers, al-Husayni organised the blockade of the 100,000 Jewish residents of Jerusalem. To counter this, the Yishuv authorities tried to supply the Jews of the city with food by using convoys of up to 100 armoured vehicles, but the operation became more and more impractical as the number of casualties in the relief convoys surged. By March, Al-Hussayni’s tactic, sometimes called “The War of the Roads”, had paid off. Almost all of Haganah’s armoured vehicles had been destroyed, the blockade was in full operation, In the last week of March, 136 supply trucks had tried to reach Jerusalem; only 41 had made it and the Haganah had lost more than 100 troops. According to Benny Morris the situation for those who dwelt in the Jewish settlements in the highly isolated Negev and North of Galilee was equally critical. 
This was the background to Plan Dalet, the growing siege of the Jewish settlement
“Arab states only intervened on May 15 because of the ethnic cleansing that has already begun in Palestine!”
Between 8 and 17 December the heads of the Arab states met in Cairo for a series of meetings, under the auspices of the Arab League, to discuss the Palestine situation. The gathering defined the overarching Arab objective as ‘obstructing the partition plan, preventing the creation of a Jewish state, and preserving Palestine as an independent unified Arab state’. To this end, the Arab states would contribute one million Egyptian pounds to the Palestine war effort (on top of the same amount promised three months earlier by another Arab League summit in the Lebanese town of Sofar), would place some 10,000 rifles at the disposal of the League’s military committee and would make the necessary arrangements for the recruitment of 3,000 volunteers for the ALA that was being established in Syria. They also reaffirmed the decision, taken at the Alei summit of October 1947, to deploy their forces along the Palestine border so long as the British remained in the country, in order to extend active support for the ALA’s operations within Palestine. 
The Arab Legion intervened in the war even before the general Arab invasion in May 1948 trained the Arabs of the Land of Israel and fought alongside them.
Abdullah al-Tel, commander of the Jerusalem Legion during the War of Independence and governor of East Jerusalem after it, testified in his memoir, after Hecht in November, when he was annexed to the First British Division, whose headquarters in Sarpand, “helped Allah fulfill my duty in the struggle in Palestine” Additional Arabs and in coordination with the heads of the local leadership of the Arabs of Palestine, including the mayor of Lod, trained young people from Lod, Ramla , Abbasiya,al-Beria… to use weapons they borrowed from the Legion’s warehouses, including ranges.
On December 14, 1947, the Legion killed 13 members of the Ben Shemen convoy while murdering helpless wounded.
On April 22, the Legion units stationed along the Jenin-Haifa road assisted the Arabs in the battle for Haifa.
Between April 27 and 29, the Legion attacked Kibbutz Gesher in an attempt to occupy it, even though Gesher was intended to be within the borders of the Jewish state according to the partition plan.
The Legion blocked the road to Jerusalem in the Latrun area (which the Jordanians held until the Six-Day War) and in the process renewed the siege of Jewish Jerusalem.
On May 12, it attacked Gush Etzion and split it in two. The bloc settlements surrendered two days later. Survivors of the massacre in Kfar Etzion went into Jordanian captivity.
This clearly shows that the decision to officially intervene on May 15 was not related to any “ethnic cleansing”, but simply a wait for the end of the British Mandate to attack the Jewish Yeshov completely exposed.
“The Arab states did not invade Israel in 1948, but only defended the Areas that were designated for the Arab State according to the UN partition plan”
(Credit to Gail Ellis)
Egypt’s air force and navy invaded Israeli air space and offshore waters to attack Tel Aviv and other areas of Israel repeatedly
The Egyptian forces on the ground attacked Kibbutzim Negba, Nirim and Urim, all inside Israel and not on the way to the Arab sector
The Jordanians attacked Gezer, Hulda and Jerusalem, which, though not in the Israeli sector was a Jewish majority city in the neutral zone.
The Lebanese army attacked Ramat Naftali, Malkiye, Kadesh, Nebi Yeshua and Zara’in, all in the Israeli sector.
Iraq attacked at Tira, inside Israel
Iraq and Syria together attacked Gesher, Ein Gev, Shar Ha Golan, Mesada and Degania.
The Syrian army attacked Kibbutz Dan and Kibbutz Dafna
Syria attacked Kibbutz Mishmar HaYardan, and the Arab Liberation Army attacked the Afula Tiberias road at Sejera, also in Israel.
“Massacres by the Zionists were widespread and supported by the leadership”
According to Benny Morris, Yishuv (or later Israeli) soldiers killed roughly 800 Arab civilians and prisoners of war in 24 incidents.
This includes incidents that have since been questioned such as Lydda and Deir Yassin
Considering the war killed over 2,000 Jewish civilians, let alone nearly 600 Jewish captives who were “slaughtered amid scenes of gang rape and sodomy… dismembered, decapitated, mutilated and then photographed.” 
“Al Zot” is a poem by Natan Alterman published in the newspaper “Davar” on November 19, 1948, when the War of Independence was in full swing. The song describes a war crime of an IDF soldier, and at the end there is a demand to prosecute war criminals and not whitewash their actions. After its publication, the song was distributed among IDF soldiers, according to a decision by David Ben-Gurion, the prime minister and defense minister. 
The Arab-Israeli Conflict: The Palestine War 1948 by Efraim Karsh page 31
 Benny Morris (2008). 1948: a history of the first Arab-Israeli war page 116
 Netanel Lorch, The Edge of the Sword: Israel’s War of Independence, 1947–1949 (New York: G.P. Putnam’s Sons, 1961), 450 (2,000 civilians); Sarah Honig, Jerusalem Post, March 1, 2001 (600 captives).