HERZLIYA, Israel, May 19 (Reuters/Dan Williams) - Iran's supreme leader and the commander of Lebanon's Hezbollah guerrillas go wide-eyed at their orders to launch a sneak attack on Tel Aviv.

Then the two wargamers -- in fact, Israeli ex-generals -- scoff in gruff Hebrew, dismissing the scenario as nonsense.

So begins Israel's latest simulation of a faceoff with a nuclear Iran: dissent about the very premise promising a lively spiral of events but, arguably, limited real-world advice. Teams playing 20 countries, coalitions and militias work through the crisis, cooped up in their headquarters -- flag-marked classrooms in the Interdisciplinary Centre (IDC), a balmy university campus at Herzliya, near Tel Aviv.

Their script calls for Tehran to have declared itself a nuclear power in 2011 and includes a surprise missile salvo by Iranian ally Hezbollah against Israel's Defence Ministry.

As it unfolds, coffee-clutching participants hold bilateral contacts in corridors or through the IDC's computer network.

Some leak information to the international media -- played by myself as part of Reuters' efforts to gain insight on how Israeli policymakers may view the Iran standoff.

I quickly understand the appeal of such events, which have become ingrained in the serious business of prestigious universities and think-tanks in Israel and the United States.

Some 40 international experts take part in the IDC game.

Tzipi Livni, former foreign minister and the leader of the centrist opposition, observes. The government of Prime Minister Benjamin Netanyahu does not -- though it will get a summary.

Wargames were once the closed-door preserve of military brass and ranking diplomats. Bringing them out into academic settings ventilates stale international debate. Vis-a-vis Iran, they give a public jaded by the Iraq and Afghan wars a rare sense of transparency over what might be the next big fight.


FRANKNESS AMONG FRIENDS

A wargame creates a storyline that is interesting for people who didn't participate, Sam Gardiner, a retired US Air Force colonel who has designed simulations for the military and the public sector, says from Washington.

The learning part is in the fact that, as they put themselves into the situation, oftentimes people will see the complexity in a way they didn't before.

According to Gardiner, the most effective wargames take 5-7 days, a duration that allows for elaborate tactical challenges to be explored, with sometimes unexpected outcomes. Off-record sessions are likelier to witness free exchanges of views.

By contrast, the IDC meeting lasts 6 hours and features just two core scenarios -- the Hezbollah salvo and revelations that the guerrillas got Iranian nuclear materials for a dirty bomb.

Gardiner's caveat about candour appears confirmed when Eitan Ben-Eliahu, a former air force chief playing the Israeli defence minister, speaks elliptically of Israel's alleged nuclear arms. He surely knows the truth about this assumed, secret arsenal.

Otherwise, there is frank consensus on Israel's limitations, especially when it comes to ties with its most important ally.

Channelling Barack Obama is Dan Kurtzer, former US envoy to Israel. His gravitas crowds the narrow administrative office serving as the White House, right next door to Syria, and Hezbollah. His team hardly touches their plate of brownies.

Realpolitik guides my circuits of the campus. Big guns count now -- world powers like the United States and China, regional brokers like Syria and Turkey, and, of course, those countries pointing big guns. I hardly see the Europeans or United Nations.

The event ends as it began, with as many questions as there are conclusions. The IDC organisers are unfazed, saying they wanted to provoke debate by positing far-reaching scenarios.