Hamas, the fundamentalist Palestinian group that rules the coastal enclave, warned after its military chief, Ahmed al-Jabari, was assassinated in an airstrike that the Israelis had "opened the gates of hell."
Israel claimed groups in Gaza have fired some 200 rockets and missiles. These reportedly included Iranian-made Fajr-5 missiles smuggled into the enclave via tunnels from Egypt's neighboring Sinai Peninsula.
One strike killed three people, the first Israeli fatalities of the current combat.
Israel intensified its airstrikes Wednesday night, saying that "approximately 100 medium-range and long-range rocket launch and infrastructure sites were targeted."
Israel's propaganda machine went into high gear too, broadcasting video footage of the airstrike that killed Jaabari that incensed the Palestinians.
Egypt, which neighbors Gaza and mediates between Hamas and Israel, announced it's recalling its ambassador. The ruling Muslim Brotherhood's political arm, the Freedom and Justice Party, called for international intervention.
The Egyptian Foreign Ministry warned the Israeli airstrikes will jeopardize regional stability, although in truth there doesn't seem to be much of that anyway.
The Israelis' major concern is that that the Muslim Brotherhood, the godfather of Islamist groups across the region and Hamas' parent organization, may retaliate by intensify demands for major modifications to the landmark Israeli-Egyptian peace agreement signed in March 1979.
Specifically, Cairo wants to end restrictions on the number of troops it can deploy in the Sinai Peninsula, a barren wasteland of desert and mountains that the Israelis see as a buffer against attack by its southern neighbor.
Most of Egypt's 82 million people have long opposed the U.S.-brokered treaty as offensive and heavily biased in favor of Israel, which they consider illegitimate and illegally occupying Palestinian land.
Israel wants to avoid heavy diplomatic pressure to renegotiate the treaty, which has been the pillar of its security policies for more than three decades.
But at the same time it cannot allow Hamas and an amalgam of other militant Palestinian factions operating in Gaza to attack its territory, particularly as the Palestinians now have rockets with increasing range and destructive power.
Egypt's Muslim Brotherhood doesn't want a war right now either as it seeks to consolidate its power following the fall of President Hosni Mubarak, who supported the peace treaty, in 2011.
But it may find itself pushed into a robust response by Egyptian public opinion.
And there's another danger. "Conflict in Gaza could trigger operations by actors outside Cairo's control," the U.S. global security consultancy Stratfor observed.
"The military, currently neutralized in the political realm, might not be content to watch from the sidelines as events unfold in Gaza."
Hamas, which has ruled Gaza since a June 2007 coup against the mainstream Palestinian organization Fatah, claims the other groups, including some inspired by al-Qaida, were behind the recent rash of rocket attacks on southern Israel, including the ports of Ashkelon and Ashdod as well as Beersheba, Israel's third largest city.
But the Israelis hold Hamas responsible for the attacks that have reached Dimona, in the Negev Desert south of Tel Aviv and the site of Israel's nuclear reactor.
Hamas also doesn't want a war right now. But extremist groups, which accuse it of abandoning the struggle against Israel to seek international legitimacy, want to undermine its influence.
If, as expected, the fighting escalates, there's a danger Hamas and the extremists in Gaza could unleash a wave of suicide bombers against Israel.
Although the Israelis haven't had to contend with suicide bombers for several years because of increased security, Palestinian "martyrdom operations" are what they fear most.
Much will depend on whether Israel decides to mount a large-scale ground operation to destroy Hamas' military infrastructure and the militants' rocket depots in the densely populated enclave.
So far, Operation Pillar of Defense has primarily involved airstrikes, one of which killed Jabari Wednesday.
But, with Syria ablaze to the north, Jordan to the east gripped by unrest and Iran seen as a major threat, the Israelis may decide they have to eliminate, for a time at least, the danger from the south.