The Sudanese transport minister, Mabrouk Mubarak Saleem, said soon afterward that a "major power bombed small trucks carrying arms, burning all of them." Unconfirmed reports at the time said the vehicles were carrying components of Iranian-made Fajr-3 missiles, which have a range of some 65 kilometers (40 miles).

A review of U.S. diplomatic cables published by WikiLeaks suggests that Iranian weapons shipments to Gaza via Sudan became an issue in 2007.

Early in 2009, Israeli Prime Minister Benjamin Netanyahu told a visiting U.S. congressional delegation: "The Egyptians know that the arms pipeline runs from Iran to Sudan to Egypt.....the Egyptians could do more to stop it, but at least they now grasp the extent of the threat."

At the same time, the deputy chief of staff of the Israel Defense Forces, Maj. Gen. Dan Harel, urged the U.S. to prod Cairo to do more, and soon, because "Hamas was getting more sophisticated weaponry from Iran, to include longer-range missiles."

Despite the convoy attack, suspicions persisted that Iran was still shipping arms to Sudan. In July 2009, the United States pressed Jordan to deny overflight rights to some planes traveling between Khartoum and Iran, including some operated by a private freight carrier, Badr Airlines, which is based in the Sudanese capital.

When presented with allegations about the Badr Airlines cargo, the Sudanese Foreign Ministry told the U.S. that the flights "were limited to carrying farm equipment and equipment for non-military manufacturing."

Not so helpful neighbor

In his last years in power, Egyptian President Hosni Mubarak became viscerally hostile to growing Iranian influence in the region.

After the last conflict in Gaza in January 2009, Israeli officials noted that Egypt had played a positive role by keeping the Rafah border closed, choking off supplies to Gaza, which was (and is) already subject to a maritime blockade.

Netanyahu then said he "looked forward" to working with the Egyptians to further blunt Hamas' capabilities, and it seemed he had a willing partner.

Egypt increased military patrols -- on the ground and in the air -- along its border with Sudan. Egyptian intelligence officials told U.S. diplomats that they had prevented Iran from transferring money to Gaza to pay the salaries of fighters for Hamas' military wing.

But according to a cable sent in April 2009 from the U.S. embassy in Cairo, longtime Egyptian intelligence chief Omar Suleiman told the chairman of the U.S. Joint Chiefs of Staff, Adm. Mike Mullen, that Iran was trying to recruit support from Sinai Bedouin tribes to facilitate arms smuggling to Gaza.

A U.S. cable sent from the Cairo embassy three months later said Mubarak's view was that "the immediate threat to Egypt comes from Iranian conspiracies with Hamas (which he sees as the "brother" of his own most dangerous internal political threat, the Muslim Brotherhood) to stir up unrest in Gaza, but he is also concerned about Iranian machinations in Sudan."

Mubarak is now long gone, and the Muslim Brotherhood is in power in Egypt. Since the latest conflict erupted, the Egyptian prime minister has visited Gaza to express solidarity with Hamas.

In addition, Sinai is largely beyond the reach of an enfeebled Egyptian state.

Sinai smugglers outwit security

"These weapons systems are being moved primarily by Sinai Bedouin criminal families. This is what they do," says Matthew Levitt of the Washington Institute for Near East Policy.

"To take them on is something that the central government in Egypt, the Morsy government, does not want to do and may not be all that capable of doing right now."

An Egyptian national security official, Usama Emam, told CNN Monday that Egypt was working hard to curb arms supplies from both Libya and Sudan.

"We have succeeded in the past months in obstructing truckloads of machine guns, anti-aircraft missiles and rockets that have passed through the Libyan border at the Saloum crossing," he said.