Israeli security chiefs, who for some time have viewed Sinai, a vast region of desert and mountains on Israel's southwestern border, as the backyard for jihadists in the Gaza Strip, now consider the region the center of what they call "an independent jihadist network."
Among the jihadist heavyweights reported to be in Sinai now is Ramzi Mowafi, an Egyptian physician who's a veteran of the 1980s Afghanistan war and was once close to the late Osama bin Laden. He escaped from an Egyptian prison in 2011.
The Long War Journal, which monitors global terrorism, reported Mowafi is believed to be coordinating militant groups and overseeing the influx of foreign jihadists into Sinai.
It reports Western officials estimate "at least several hundreds jihadists, some of whom are from Yemen and Somalia, are operating in Sinai." The Egyptians allege there are Algerians and Libyans there too.
Jihadist veteran, Mohamed Jamal al-Kashef, was captured in Cairo in October 2012. He's an Egyptian who once fought alongside al-Qaida supremo Ayman al-Zawahiri, one-time leader of Egypt's Islamic Jihad, in Afghanistan.
Al-Kashef told his Egyptian interrogators: "We consider Sinai the next frontier of conflict with the Zionists and the Americans."
The Americans say al-Kashef was a significant player in the Sept. 11, 2012, attack in Benghazi, Libya, in which U.S. Ambassador Christopher Stevens and three other Americans were killed.
Al-Kashef fought alongside Zawahiri and other Islamic Jihad members against then-Egyptian President Hosni Mubarak's police state in the 1990s.
He reportedly has links to al-Qaida in the Islamic Maghreb, al-Qaida's expanding North African affiliate, and Nasir al-Wuhayshi, leader of al-Qaida in the Arabian Peninsula, branded by Washington as al-Qaida's most dangerous outfit.
Egyptian intelligence got onto al-Kashef's trail after security forces smashed a jihadist cell in Nasr City, an upper class Cairo suburb, Oct. 24, 2012.
Jihadist groups established themselves in the Sinai following the February 2011 downfall of Mubarak, who ruthlessly crushed an Islamist insurgency in the 1990s and imprisoned tens of thousands of suspected activists.
Sinai has long been neglected by the Cairo regime and the marginalized, disgruntled Bedouin tribesmen were easily recruited by the jihadists.
With the collapse of Moammar Gadhafi's regime in Libya, Egypt's western neighbor, plundered weapons poured into Sinai.
The Israelis have also come under attack from Sinai-based jihadists and amid the political turmoil in Egypt fear their historic 1979 peace treaty with Egypt, the linchpin of Israel's entire security strategy and never popular in Egypt, could be in danger.
These days, Israel counts on Egypt's military rulers, led by Defense Minister and army chief Gen. Abdel Fattah al-Sisi, to crack down on the jihadist groups.
By all accounts, the Egyptian military is hitting the jihadists hard in a major offensive and showing little mercy.
The deployment of armor, Apache helicopter gunships and 20,000 troops "marks the greatest Egyptian military concentration in the region since the 1973 war with Israel," analyst Andrew McGregor observed in the journal Terrorism Monitor.
The army says it's killed or captured hundreds of jihadists, but the militants are retaliating and the threat, rather than diminishing, appears to be intensifying.
Egypt's generals fear the Sinai insurgency will connect with the Islamist upheaval across Egypt that followed the army's July 3 ouster of President Mohamed Morsi, a leading member of the Muslim Brotherhood.
Morsi, Mubarak's successor, was Egypt's first democratically elected head of state.
The generals' fears seem justified. On Sept. 5, jihadists of Ansar Bayt al-Maqdis, or Ansar Jerusalem, based in the Sinai, took their campaign into the Egyptian capital itself.
They tried to assassinate Interior Minister Mohamed Ibrahim, a stalwart of Egypt's security establishment, in a suicide bombing near his Cairo home.
Ansar Jerusalem claimed responsibility. On Saturday, it released a 31-minute video on the operation that showed the bomber, former Egyptian army major Walid Badr, denouncing the military for "waging war on Islam."
Egyptian security officials say Badr was trained by al-Kashef in Libya.
Since then, jihadists have attacked in the Ismaili industrial zone on the western bank of the Suez Canal in the Nile Delta, the Egyptian heartland, and in southern Sinai where Egypt's economically important Red Sea resorts present soft targets.