TEL AVIV -- When Israel assassinated the top Hamas military commander in Gaza on Wednesday, setting off the current round of fierce fighting, it was aiming not just at a Palestinian leader but at a supply line of rockets from Iran that have for the first time given Hamas the ability to strike as far as Tel Aviv and Jerusalem.
The commander, Ahmed al-Jabari, had shifted Hamas's low-grade militia into a disciplined force with sophisticated weapons like Fajr-5 rockets, which are named after the Persian word for dawn and have significantly increased the danger to Israel's major cities. They have a range of about 45 miles and are fired by trained crews from underground launching pads.
Hamas had perhaps 100 of them until the Israeli attacks last week, which appear to have destroyed most of the stockpile. The rockets are assembled locally after being shipped from Iran to Sudan, trucked across the desert through Egypt, broken down into parts and moved through Sinai tunnels into Gaza, according to senior Israeli security officials.
The smuggling route involves salaried employees from Hamas along the way, Iranian technical experts traveling on forged passports and government approval in Sudan, Israeli officials said.
Mr. Jabari's strategy has been so effective and alarming for Israel that it is preparing for a possible next stage in the four-day-old battle: a ground war in which its troops would seek to destroy remaining rocket launching bases and crews and munitions factories.
Under Mr. Jabari, Hamas also developed its own weapons industry in Gaza, building long-range rockets as well as drones that they hoped to fly over Israel just as Israeli drones roam the skies of Gaza, sowing fear in its population.
The current operation to eliminate the Hamas rocket launchers could serve to cripple the ability of Iran's allies in Gaza from retaliating should Israel ever carry out its threat to attack Iranian nuclear facilities.
"Both Hamas and Islamic Jihad are building weapons with experts from Iran," one top security official said Saturday, speaking on condition of anonymity. "What we took care of last night was their own production facility for U.A.V.'s," he added, referring to unmanned aerial vehicles, or drones. "This was all the work of Jabari, who was a very sophisticated and strategic thinker."
A number of recent Israeli military attacks were aimed at cutting the supply chain into Gaza. In late October, a munitions factory in Sudan was hit from the air. Israel did not acknowledge carrying out the attack, but the winks and nods of officials here make clear that it did. Israel has carried out several other such attacks on Sudan, including on convoys, in the past few years.
In addition, Mossad agents killed a Hamas official in a Dubai hotel in early 2010 because he was thought to be crucial to the Hamas supply chain of weapons and rockets into Gaza.
One official here said that until Israel ended its military occupation of Gaza in 2005, there were only primitive weapons factories there. The Hamas rockets had a flight capacity of about a mile, they could not be aimed and they flew in a wild cylindrical pattern. Hamas then built better rockets that could fly up to 12 miles.
That changed little until 2007, when Hamas fighters pushed the Fatah-dominated Palestinian Authority out of Gaza into the West Bank and took over governing the coastal strip.
"At that point, Jabari turned his neighborhood defense operation into a real army," said a retired Israeli general whose portfolio included Gaza and who spoke on condition of anonymity. "He organized what was a militia into companies, battalions and brigades. He sent commanders to Syria and to Iran to be trained by the Revolutionary Guards. And then he built up this whole new branch to develop military technology focusing on long-range missiles."
The collapse of the government of Col. Muammar el-Qaddafi in Libya last year created other supply options for Hamas as Libyan military storehouses were raided and the equipment sold off. Those weapons were driven across Egypt and into Gaza.
It remains to be seen whether Mr. Jabari's death will truly cripple Hamas, or whether it will find someone equally adept to take his place, the officials said.
Either way, Hamas now has a range of rockets and weapons in its arsenal, said Jeffrey White, a former analyst with the United States Defense Intelligence Agency and now a fellow at the Washington Institute for Near East Policy.
In addition to the Fajr-5, Hamas has a few hundred of what are known as enhanced Grad rockets, which have a range of about 25 miles. The Grads are 122-millimeter rockets that have bigger warheads than the standard Grads, but their accuracy is relatively low. The Grads may also be coming from Iran, Mr. White said, but others are made in Gaza and imported from Libya.
In addition, Hamas has hundreds of standard Grads that have a range of about 12 miles, as well as thousands of homemade mortars and Qassam rockets with a range of about six miles.
Israeli officials said the movement of the Fajr-5 rockets through Egypt could not go unnoticed there, given their size. Each is 20 feet long and weighs more than 2,000 pounds -- the warhead alone weighs 375 pounds -- and the trucks carrying them across Egyptian bridges and through roadblocks into Sinai would be hard to miss.
In the current conflict, Israel's antirocket system, known as Iron Dome, has been more effective than expected, but still dozens of rockets have landed.
Whether the military operation against Gaza is a dress rehearsal for any future attack on either Iran or Lebanon -- where Hezbollah has thousands of rockets pointed at Israel -- is a matter under debate here. Some see it as clearing away any possible trouble from Gaza. Others say that makes little sense, given the difference of scale in the conflict in Gaza and any war against Iran or Hezbollah. Hamas's arsenal is tiny compared with what Hezbollah in Lebanon is thought to have: thousands of rockets capable of hitting Tel Aviv.
Yonatan Touval, an analyst with Prime Source, a private Tel Aviv risk-assessment company, said, "The Iron Dome system is ineffective in intercepting longer-range projectiles, such as those that would be launched from Lebanon toward the Tel Aviv area. To address this threat, Israel is currently developing the Magic Wand system, but it is not expected to become operational before 2015."
He added that the fighting now was therefore not really a test of a future conflict involving Iran and Lebanon. "If Israel's political leadership is treating the current operation in Gaza as something of a rehearsal for a future war with Hezbollah and Iran, it is rehearsing the wrong play," he said.
Michael R. Gordon contributed reporting from Washington.
This article originally appeared in The New York Times.