Mahmoud Zahar, a senior Hamas official in Gaza, refused in an interview to take direct responsibility for ordering the Egyptian border opened, but said: “We are creating facts. We have to try to change the situation, and now we await the results.”

With the crossings to Israel closed and minimal goods coming in, Mr. Zahar said: “Rafah is our only lung. If Rafah remains shut, it means our acceptance to be strangled, our acceptance to die. We warned the Egyptians yesterday that people are hungry and dying.” Sometimes, he acknowledged, it was necessary to create a crisis to settle another one.

It was clear that Hamas, pressed by the closing from Israel, which had produced international protests, decided to push the issue with Egypt. Muhammad Mishlahad broke down nearly a half-mile of massive concrete blocks with his big Effer crane. “I got a call from Hamas at 6 a.m. this morning and they said they had a job for me,” Mr. Mishlahad said, nearly giddy with the thrill of the day. “They asked me to come and clear the barrier.” Asked if he was afraid, he laughed and said: “Why should we be afraid? This is our state.”

Image Palestinians climbed over a section of the wall at Rafah that had been torn down Wednesday morning on orders from Hamas. Credit... Ali Ali/European Pressphoto Agency

In Cairo, analysts said that the situation was delicate for the Egyptian authorities. “It is a dilemma for Egypt,” said Emad Gad, an analyst at the Ahram Center for Political and Strategic Studies. “If it prevents Palestinian civilians from crossing and confronts them with force, it opens itself up to unlimited public scrutiny at home. And if it lets the Palestinians through, they face the risk of not knowing who or what is coming in and criticism from Israel and the United States.”

Here in Rafah, relatives from both sides met, as did business partners who usually smuggle goods through tunnels from Egypt to Gaza. For one day at least, and probably longer, no tunnels were necessary, and Egyptian businessmen brought in goods to sell from the more distant town of El Arish. Some enterprising Gazans ordered goods from Cairo in the morning and went across to Rafah to pick them up at noon.

Farid Abu Jabara, 45, who helps to run a Swedish foundation for Gaza’s handicapped, picked up 50 air mattresses and their pumps, which he had ordered at his own initiative from Cairo at 7 a.m.