JERUSALEM — Israel's surprise air assault on Gaza Strip militants killed the top military commander of Hamas and set the rivals on a familiar course that could end with another major confrontation — but in unpredictable new circumstances created by the "Arab Spring."

Compared with its past campaigns against Hamas, Israel is likely to find itself more restrained politically and militarily in the new landscape.

Rather than being able to count on former Egyptian President Hosni Mubarak to help isolate Hamas, as he did during a 22-day operation four years ago, Israel must weigh whether another large-scale Gaza offensive would endanger the landmark 1979 peace accord with Egypt, which has long served as a cornerstone of regional stability.

By Wednesday evening, Egypt's new Islamist president, Mohamed Morsi, announced he was recalling the country's ambassador to Israel to protest the assault on the Palestinian territory.

"It's a completely new game for Israel," said Yoram Meital, an Egypt expert at the Herzog Center for Middle East Studies and Diplomacy at Ben-Gurion University. "The equation before was between Israel and the Palestinians. Now it's a triangle, involving Egypt too."

Israel's offensive four years ago killed 1,200 Palestinians, but Mubarak brushed aside his own people's support for besieged Gazans and helped Israel seal Gaza's border.

The course of Israel's military campaign could be shaped by Morsi's decisions, analysts say.

Unlike his deposed predecessor, Morsi will find it difficult to ignore the anti-Israel mood of the Egyptian street. Israel is worried Egypt might open the Rafah border crossing to humanitarian aid or even Islamic fighters to help Gazans, Meital said.

"Israel is taking a very bold risk here because if this campaign continues, it could be gambling with the relationship with Egypt," he said.

Both Hamas, which has been emboldened by the new Egyptian government, and Israel, which has clashed repeatedly with it, will be watching closely to see whether Morsi comes out more strongly against Israel in the coming days or adopts a more pragmatic approach, perhaps trying to broker a cease-fire.

Besides public sentiment, Morsi must take into account his relationship with the United States and other world powers. He is seeking billions of dollars in aid and investment from the West to help the Egyptian economy. Some analysts say that even though Morsi will have to respond to be a credible Arab leader, Egyptians are more concerned with domestic problems.

Egyptian tribal leaders have blamed Hamas and other Palestinian groups for aiding the resurgence of deadly militant networks in the Sinai peninsula, who have attacked Egyptian government forces there.

Although he recalled his ambassador, Morsi did not immediately comment in public. But other leaders in the Muslim Brotherhood organization said the country would not tolerate another Israeli campaign in Gaza.

"The brutal aggression on Gaza proves that Israel has not yet learned that Egypt has changed," said Saad Katatni, head of the Muslim Brotherhood's Freedom and Justice Party.

Israeli military officials said the assault could last several days. The campaign is aimed at "defending the people of Israel who have been under rocket attack and crippling terrorist organizations' capabilities," said Israel Defense Forces spokeswoman Lt. Col. Avital Leibovitz.

Tension between Israel and Gaza militants has been mounting for nearly a week, following a missile attack against an Israeli jeep along the Gaza border that left four soldiers wounded.

In the ensuring back-and-forth violence, Hamas and other militant groups fired more than 120 rockets and mortar rounds into southern Israel, injuring several Israeli civilians and damaging property.

Israeli Prime Minister Benjamin Netanyahu has faced growing pressure to move aggressively to stop the attacks, which have terrified nearly 1 million southern Israelis and crippled daily activities.

Over the last year, Hamas, an offshoot of the Muslim Brotherhood, has resumed a more hostile stance toward Israel, betting that Morsi's election would strengthen its hand.

After observing a self-imposed cease-fire for most of the last four years, militants in recent months increased their attacks on Israel, using new types of weaponry acquired in Libya last year after the chaotic fall of Moammar Kadafi, such as antitank and antiaircraft missiles.