Hezbollah has long possessed rockets capable of striking deep within Israel, but they are more liable to land harmlessly in empty fields than to hit their target. In recent years, Iran has developed missiles with significantly improved accuracy—and Israel has focused on destroying them.

For Israeli officials, this new threat is embodied in the Fateh-110, a missile produced by Iran that retrofits long-range rockets with advanced guidance systems, allowing Hezbollah to make good on its threats. In the 2006 war, Hezbollah learned that unguided rockets could spark panic and mass evacuations among civilians, but were far less effective for striking military targets or critical infrastructure. While the Fateh-110 is not yet a precision missile, it is undoubtedly a more accurate weapon. Hajj Mohammed’s unguided rockets, if fired at Tel Aviv, would be just as likely to hit a point within 3.6 kilometers of his target as to land outside that zone. The Fateh-110, by comparison, whittles that margin of error down to roughly one kilometer.

Such missiles could still bring life in Tel Aviv and Jerusalem to a standstill and shut down Ben Gurion Airport. But they would not be accurate enough to destroy specific military targets. “I don’t think these newer capabilities that Iran is demonstrating will be militarily decisive,” said Michael Elleman, a senior fellow at the International Institute for Strategic Studies. “But it will complicate Israeli plans significantly.”

Iran’s missile capabilities, however, are improving every year. It could develop more advanced technology to regulate its missiles’ thrust, and outfit them with GPS systems. Perhaps more worrisome for the Israelis: Elleman said there is evidence that the Iranians are trying to miniaturize some of their guidance components, which could make some of Hezbollah’s smaller rockets more accurate as well. “It’s the direction in which this is all moving that is probably more worrying than their actual capacity today,” he said.

The Hezbollah leader Hassan Nasrallah has said that his group has transferred at least some Fateh-110s to Lebanon. Israeli defense officials have also expressed concern that the group maintains control of some of these missiles in the rugged, mountainous terrain of western Syria, allowing it to potentially strike Israel without igniting an all-out war in Lebanon. Israeli airstrikes against Hezbollah in Syria, meanwhile, could ignite the next war.

The damage done to Israel in another war will pale in comparison to the destruction wrought on Lebanon. Under a strategy outlined in 2008 that calls for the use of disproportionate force on any villages or neighborhoods in which Hezbollah operates, Lebanon would experience a level of destruction that “has not been seen since World War II,” one Israeli defense official was quoted in an International Crisis Group report as saying. “We will crush it and grind it to the ground.”