1948 Palestine war
In December 1947, immediately following the UN partition vote, the 1947–1948 Civil War in Mandatory Palestine broke out between the Yishuv and Palestinian Arabs. The Irgun fought together with the Haganah and Lehi during that period. Notable operations in which they took part were the battle of Jaffa and the Jordanian siege on the Jewish Quarter in the Old City of Jerusalem. The Irgun's most controversial operation during this period, carried out alongside Lehi, was an assault on the Arab village of Deir Yassin in which more than a hundred villagers and four of the attackers were killed. The event later became known as the Deir Yassin massacre, though Irgun and Lehi sources would deny a massacre took place there. Begin also repeatedly threatened to declare independence if the Jewish Agency did not do so.
Throughout the period of the rebellion against the British and the civil war against the Arabs, Begin lived openly under a series of assumed names, often while sporting a beard. Begin would not come out of hiding until April 1948, when the British, who still maintained nominal authority over Palestine, were almost totally gone. During the period of revolt, Begin was the most wanted man in Palestine, and MI5 placed a 'dead-or-alive' bounty of £10,000 on his head. Begin had been forced into hiding immediately prior to the declaration of revolt, when Aliza noticed that their house was being watched. He initially lived in a room in the Savoy Hotel, a small hotel in Tel Aviv whose owner was sympathetic to the Irgun's cause, and his wife and son were smuggled in to join him after two months. He decided to grow a beard and live openly under an assumed name rather than go completely into hiding. He was aided by the fact that the British authorities possessed only two photographs of his likeness, of which one, which they believed to be his military identity card, bore only a slight resemblance to him, according to Begin, and were fed misinformation by Yaakov Meridor that he had had plastic surgery, and were thus confused over his appearance. Due to the British police conducting searches in the hotel's vicinity, he relocated to a Yemenite neighborhood in Petah Tikva, and after a month, moved to the Hasidof neighborhood near Kfar Sirkin, where he pretended to be a lawyer named Yisrael Halperin. After the British searched the area but missed the street where his house was located, Begin and his family moved to a new home on a Tel Aviv side street, where he assumed the name Yisrael Sassover and masqueraded as a rabbi. Following the King David Hotel bombing, when the British searched the entire city of Tel Aviv, Begin evaded capture by hiding in a secret compartment in his home. In 1947, he moved to the heart of Tel Aviv and took the identity of Dr. Yonah Koenigshoffer, the name he found on an abandoned passport in a library.
In the years following the establishment of the State of Israel, the Irgun's contribution to precipitating British withdrawal became a hotly contested debate as different factions vied for control over the emerging narrative of Israeli independence. Begin resented his portrayal as a belligerent dissident.
After the Israeli Declaration of Independence on 14 May 1948 and the start of the 1948 Arab–Israeli War, Irgun continued to fight alongside Haganah and Lehi. On 15 May 1948, Begin broadcast a speech on radio declaring that the Irgun was finally moving out of its underground status. On 3 June Begin signed an agreement with the provisional government headed by David Ben-Gurion, where the Irgun agreed to formally disband and to integrate its force with the newly formed Israel Defense Forces (IDF), but was not truthful of the armaments aboard the Altalena as it was scheduled to arrive during the cease-fire ordered by the United Nations and therefore would have put the State of Israel in peril as Britain was adamant the partition of Jewish and Arab Palestine would not occur. This delivery was the smoking gun Britain would need to urge the UN to end the partition action.
Intense negotiations between representatives of the provisional government (headed by Ben-Gurion) and the Irgun (headed by Begin) followed the departure of Altalena from France. Among the issues discussed were logistics of the ship's landing and distribution of the cargo between the military organizations. Whilst there was agreement on the anchoring place of the Altalena, there were differences of opinion about the allocation of the cargo. Ben-Gurion agreed to Begin's initial request that 20% of the weapons be dispatched to the Irgun's Jerusalem Battalion, which was still fighting independently. His second request, however, that the remainder be transferred to the IDF to equip the newly incorporated Irgun battalions, was rejected by the Government representatives, who interpreted the request as a demand to reinforce an "army within an army."
The Altalena reached Kfar Vitkin in the late afternoon of Sunday, 20 June. Among the Irgun members waiting on the shore was Menachem Begin, who greeted the arrivals with great emotion. After the passengers had disembarked, members of the fishing village of Mikhmoret helped unload the cargo of military equipment. Concomitantly with the events at Kfar Vitkin, the government had convened in Tel Aviv for its weekly meeting. Ben-Gurion reported on the meetings which had preceded the arrival of the Altalena, and was adamant in his demand that Begin surrender and hand over all of the weapons:
We must decide whether to hand over power to Begin or to order him to cease his separate activities. If he does not do so, we will open fire! Otherwise, we must decide to disperse our own army.
The debate ended in a resolution to empower the army to use force if necessary to overcome the Irgun and to confiscate the ship and its cargo. Implementation of this decision was assigned to the Alexandroni Brigade, commanded by Dan Even (Epstein), which the following day surrounded the Kfar Vitkin area. Dan Even issued the following ultimatum:
To: M. BeginBy special order from the Chief of the General Staff of the Israel Defense Forces, I am empowered to confiscate the weapons and military materials which have arrived on the Israeli coast in the area of my jurisdiction in the name of the Israel Government. I have been authorized to demand that you hand over the weapons to me for safekeeping and to inform you that you should establish contact with the supreme command. You are required to carry out this order immediately. If you do not agree to carry out this order, I shall use all the means at my disposal in order to implement the order and to requisition the weapons which have reached shore and transfer them from private possession into the possession of the Israel government. I wish to inform you that the entire area is surrounded by fully armed military units and armored cars, and all roads are blocked. I hold you fully responsible for any consequences in the event of your refusal to carry out this order. The immigrants – unarmed – will be permitted to travel to the camps in accordance with your arrangements. You have ten minutes to give me your answer.D.E., Brigade Commander
The ultimatum was made, according to Even, "in order not to give the Irgun commander time for lengthy considerations and to gain the advantage of surprise." Begin refused to respond to the ultimatum, and all attempts at mediation failed. Begin's failure to respond was a blow to Even's prestige, and a clash was now inevitable. Fighting ensued and there were a number of casualties. In order to prevent further bloodshed, the Kfar Vitkin settlers initiated negotiations between Yaakov Meridor (Begin's deputy) and Dan Even, which ended in a general ceasefire and the transfer of the weapons on shore to the local IDF commander.
Begin had meanwhile boarded the Altalena, which was headed for Tel Aviv where the Irgun had more supporters. Many Irgun members, who joined the IDF earlier that month, left their bases and concentrated on the Tel Aviv beach. A confrontation between them and the IDF units started. In response, Ben-Gurion ordered Yigael Yadin (acting Chief of Staff) to concentrate large forces on the Tel Aviv beach and to take the ship by force. Heavy guns were transferred to the area and at four in the afternoon, Ben-Gurion ordered the shelling of the Altalena. One of the shells hit the ship, which began to burn. Yigal Allon, commander of the troops on the shore, later claimed only five or six shells were fired, as warning shots, and the ship was hit by accident.
There was danger that the fire would spread to the holds which contained explosives, and Captain Monroe Fein ordered all aboard to abandon ship. People jumped into the water, whilst their comrades on shore set out to meet them on rafts. Although Captain Fein flew the white flag of surrender, automatic fire continued to be directed at the unarmed survivors swimming in the water. Begin, who was on deck, agreed to leave the ship only after the last of the wounded had been evacuated. Sixteen Irgun fighters were killed in the confrontation with the army (all but three were veteran members and not newcomers in the ship); six were killed in the Kfar Vitkin area and ten on Tel Aviv beach. Three IDF soldiers were killed: two at Kfar Vitkin and one in Tel Aviv.
After the shelling of the Altalena, more than 200 Irgun fighters were arrested. Most of them were released several weeks later, with the exception of five senior commanders (Moshe Hason, Eliyahu Lankin, Yaakov Meridor, Bezalel Amitzur, and Hillel Kook), who were detained for more than two months, until 27 August 1948. Begin agreed the Irgun soldiers would be fully integrated with the IDF and not kept in separate units.
About a year later, Altalena was refloated, towed 15 miles out to sea and sunk.