After the 1967 Six-Day War, Palestinian fedayeen guerrillas relocated to Jordan and stepped up their attacks against Israel and what had become the Israeli-occupied West Bank. They were headquartered at the Jordanian border town of Karameh, which Israel targeted during the Battle of Karameh in 1968, leading to a surge of Arab support for the fedayeen. The PLO's strength grew, and by early 1970, leftist groups within the PLO began calling for the overthrow of Jordan's Hashemite monarchy, leading to violent clashes in June 1970. Hussein hesitated to oust them from the country, but continued PLO activities in Jordan culminated in the Dawson's Field hijackings of 6 September 1970. This involved the Popular Front for the Liberation of Palestine (PFLP) seizing three civilian passenger flights and forcing their landing in the Jordanian city of Zarqa, where they took foreign nationals as hostages and blew up the planes in front of international press. Hussein saw this as the last straw and ordered the Jordanian Army to take action.
On 17 September 1970, the Jordanian Army surrounded cities with a significant PLO presence, including Amman and Irbid, and began targeting fedayeen posts that were operating from Palestinian refugee camps. The next day, 10,000 Syrian troops bearing Palestine Liberation Army (PLA) markings began an invasion by advancing towards Irbid, which the fedayeen had occupied and declared to be a "liberated" city. On 22 September, the Syrians withdrew from Irbid after suffering heavy losses to a coordinated aerial–ground offensive by the Jordanians. Mounting pressure from other Arab countries, such as Iraq, led Hussein to halt his offensive. On 13 October, he signed an agreement with Arafat to regulate the fedayeen's presence in Jordan. However, the Jordanian military attacked again in January 1971, and the fedayeen were driven out of the cities, one by one, until 2,000 surrendered after they were encircled during the Ajlun offensive on 23 July, formally marking the end of the conflict.
Jordan allowed the fedayeen to relocate to Lebanon via Syria, where they later became involved in the Lebanese Civil War. The Palestinian Black September Organization was founded after the conflict to carry out attacks against Jordanian authorities in response to the fedayeen's expulsion; their most notable attack was the assassination of Jordanian prime minister Wasfi Tal in 1971, as he had commanded parts of the military operations against the fedayeen. The following year, the organization shifted its focus to attacking Israeli targets and carried out the Munich massacre against Israeli athletes. Though the events of Black September did not reflect a Jordanian–Palestinian divide, as there were Jordanians and Palestinians on both sides of the conflict, it paved the way for such a divide to emerge subsequently.
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