In the early morning hours of May 15, 1948, Egyptian forces crossed the international border separating Israel and Egypt, and advanced in two columns: one North along the coastal Road and the other South-east towards Beer Sheba.
On the night of May 14-15, the Egyptians attempted once again to conquer Kfar Darom, a religious kibbutz 7 miles (11 km) south of Gaza. A previous Egyptian attack on May 10th was repelled, after several assault attempts had been beaten back by the defenders. In one such attempt defenders who lacked grenades filled their phylacteries (tfillin) bags with TNT and threw them at the Egyptian troops. Reinforcements sent to support the defenders ran into an Egyptian force which prevented their arrival to the kibbutz. The Kfar Darom defenders, however, succeeded in pushing back the attackers who avoided launching additional attacks on the kibbutz.
At the same time that Kfar Darom was attacked, Syrian forces attacked Kibbutz Nirim, further south. However, Israeli forces succeeded in repelling the attackers and in inflicting heavy casualties on them. As a result of this failure, the Egyptians came to the realization that any attack launched on the Jewish forces would exhaust their troops. The Egyptians continued their advance, and headed towards Tel Aviv, and reached Kibbutz Yad Mordechai, which was situated on the main road to Tel Aviv.
May 19: Attack on Yad Mordechai
The need to concentrate large-scale forces caused the Egyptians to delay their May 19th attack on kibbutz Yad Mordechai. Egyptian forces included two infantry battalions, one armored battalion and one artillery regiment. The attack began with an artillery softening-up. After three hours of hard fighting, the Egyptians forces managed to infiltrate into the farm yard. In bitter hand-to-hand fighting, the defenders, who together with reinforcements from the Negev Brigade numbered no more than a company, succeeded in repelling the attackers. The attack was renewed the following day. That same day, the defenders of the settlement managed to repel four Egyptian attacks, one after the other. On May 22 1948, the Yad Mordechai defenders informed the Southern Command Staff that: "The strength of our fighters is weakening, the forces are exhausted. We fear that Yad Mordechai will fall as did Kfar Etzion. Either evacuate the kibbutz or dispatch support. It is imperative that the women and wounded be evacuated immediately."
Following a number of additional Egyptian attacks, the Southern Command Staff decided to withdraw. With morning twilight on the 24th of May, Yad Mordechai kibbutz members withdrew kibbutz Gevaram. The conquest of Yad Mordechai cost the Egyptian forces approximately 400 losses. In addition, during the five days that it took the Egyptians to capture Yad Mordechai, Israeli forces were able to build a defense line North of Ashdod.
The fall of Yad Mordechai opened up to the interior of Israel to the Egyptian forces. The "Givati" Brigade had taken part in the fighting around the Jerusalem "corridor." The Brigade returned to the South the day following the Egyptian invasion. Two days later, the Brigade launched an operation to mop-up the sector. The Sarafand (Tserifin) camp was captured on the night between the 19th and 20th of May.
In the afternoon hours of May 21, 1948 kibbutz Negbah was attacked by an Egyptian armored column and strafed from the air.
Sources: Israel Defense Forces