TWO evenings a month, four dozen defence and intelligence officials gather in an undisclosed building in Virginia. They chat informally about “what if” scenarios. For example: what if Israel were to bomb Iran’s nuclear sites? Recent chats on this topic have been fruitful for a surprising reason, says John Patch, a member of the Strategic Discussion Group, as it is called. Nearly a quarter of those who regularly attend play a board game called “Persian Incursion”, which deals with the aftermath of just such an attack. For half the players, such games are part of their job.

You don’t need a security clearance to play Persian Incursion. Anyone can order it from Clash of Arms, a Pennsylvania firm that makes all kinds of games, from Epic of the Peloponnesian War to Pigs in Space. Yet playing a war game is like receiving an intelligence briefing, Mr Patch says. It forces players to grapple with myriad cascading events, revealing causal chains they might not imagine. How might local support for Iran’s regime be sapped if successful Israeli raids strengthen claims that its anti-aircraft batteries were incompetently sited? Might a photo purportedly showing Iran’s president with a prostitute help the Saudi monarchy contain anti-Jewish riots? Might those efforts be doomed if the photo were revealed as a fake?

Paul Vebber, a gameplay instructor in the navy, says that in the past decade the government has started using strategy board games much more often. They do not help predict outcomes. For that, the Pentagon has forecasting software, which it feeds with data on thousands of variables such as weather and weaponry, supply lines, training and morale. The software is pretty accurate for “tight, sterile” battles, such as those involving tanks in deserts, says an intelligence official. Board games are useful in a different way. They foster the critical but creative thinking needed to win (or avoid) a complex battle or campaign, he says.

Some games are for official use only. The Centre for Naval Analyses (CNA), a federally funded defence outfit, has created half a dozen new ones in the past two years. Most were designed by CNA analysts, but commercial designers occasionally lend a hand, as they did for Sand Wars, a game set in north-west Africa.

CNA games address trouble in all kinds of places. In Transition and Tumult, designed for the marine corps, players representing groups in Sudan and South Sudan try to whip up or quell local unrest that might lead American forces to intervene. In The Operational Wraparound, made for the army, players struggle to stoke or defeat a Taliban insurgency in Afghanistan. Avian Influenza Exercise Tool, a game designed for the Department of Agriculture, shows health officials how not to mishandle a bird-flu epidemic.

Board games designed for the government typically begin as unclassified. Their “system”, however, becomes classified once players with security clearances begin to incorporate sensitive intelligence into it, says Peter Perla, a game expert at CNA. If an air-force player knows that, say, a secret bunker-busting bomb is now operational, he can improve the dice-roll odds that a sortie will destroy an underground weapons lab. During official gaming sessions, analysts peer over players’ shoulders and challenge their reasoning. Afterwards, they incorporate the insights gleaned into briefings for superiors.

One reason why board games are useful is that you can constantly tweak the rules to take account of new insights, says Timothy Wilkie of the National Defence University in Washington, DC. With computer games, this is much harder. Board games can also illuminate the most complex conflicts. Volko Ruhnke, a CIA analyst, has designed a series of games about counterinsurgency. For example, Labyrinth: The War on Terror, 2001-? (sold by GMT Games of California) models “parallel wars of bombs and ideas”, as one reviewer puts it, on a board depicting much of Eurasia and Africa.

Even training for combat itself can be helped with dice and cards. Harpoon, a game about naval warfare, has proved so accurate in the past that hundreds of Pentagon officials will play it when the next version comes out in a couple of years, says Mr Patch. One of its designers, Chris Carlson, is also responsible for the “kinetic” aspects of Persian Incursion (ie, the bits that involve shooting). Mr Carlson is a former Defence Intelligence Agency analyst; Persian Incursion’s data on the nuts and bolts of assembling and commanding bomber, escort, and refuelling aircraft “strike packages” for destroying Iran’s nuclear sites is so precise that on at least two occasions intelligence officials have suggested that he is breaking the law by publishing it.