Israeli infiltration into Jordanian territory at this time included retaliatory raids by military units at Qibya and Nahhalin. Israel's frustration with the UN and the other parties led to their withdrawal from ISMAC in 1951 and HKJIMAC in 1954. The functioning of the Israel-Lebanon MAC remained smooth due to the more relaxed attitude of the Israeli patrols towards returnees and infiltrators. Disputes with Egypt, who banned Israel-bound shipping from the Suez Canal and blockaded the Gulf of Aqaba, pertained to the al-Auja DMZ. By 1955, Egypt's sponsorship of Palestinian fedayeen (self-sacrificer) raids caused Israel to cease attending the Egyptian MAC and to step up raids into the Gaza Strip and Sinai, which resulted in Egypt arming the fedayeen. From 21 September 1955, the Egypt/Israel demilitarized zone was occupied by Israel armed forces. In response, Secretary-General Dag Hammarskjöld and the Chief of Staff UNTSO attempted to secure the implementation of a plan for withdrawal of Israeli armed forces and the removal of Egyptian forces from prohibited positions. Articles VII and VIII of the Egypt-Israel GAA established a Demilitarized Zone (DMZ) centred on El-Auja and forbade the presence of armed forces. It also prohibited Egypt from maintaining positions in an adjoining area west of the demilitarized zone, and limited the arms and troops in the Defensive Areas on both sides of the Line. Both Egypt and Israel had indicated to the Secretary-General their willingness to comply fully with these two articles, within the framework of a return to full compliance with the Armistice Agreement. The Israeli Government gave assurances of its complete acceptance in principle of the plan. The agreed withdrawal, however, never took place. The 1956 invasion of Egypt by British, French and Israeli forces, followed Egypt's decision on 26 July 1956 to nationalize the Suez Canal.