Exporting the Islamic revolution was enshrined in the Iranian constitution Khomeini helped to draft in 1979, and Ahmadinejad has been one of its most enthusiastic supporters. One of the more telling revelations to come out of Israel's invasion of Gaza has been to expose the level of Iran's support for Hamas which, like Tehran, is totally opposed to any political accommodation with Israel. Before the crisis it was well known that most of Hamas's training and funding came from Iran, and that hundreds of Hamas militants had passed through the Revolutionary Guards' training camps there. But it was the scale of the military technology that Iran had managed to smuggle into Israel through the various underground tunnel networks that was the big surprise. Previously Hamas had been obliged to make do with primitive, home-made Kassam rockets, which have a range of only a few kilometres, to attack southern Israel. But thanks to Tehran, Hamas now has the capability to fire medium-range Grad missiles that can hit major centres of Israeli population such as Ashdod, Ashkelon and Beersheva.

Iran's support for Hamas, which has increased significantly under Ahmadinejad, is in many ways a replica of its support for the militant Shia Muslim Hizbollah in southern Lebanon. Indeed, it was Ahmadinejad's decision to increase Iran's military support for Hizbollah that provoked the 2006 war with Israel. Nor have Iran's revolutionary activities under Ahmadinejad been confined to intimidating Israel's northern and southern borders. After he became president, coalition commanders in both Iraq and Afghanistan recorded a dramatic increase in Revolutionary Guard activity in trying to undermine coalition attempts to support the pro-Western, and democratically elected, governments.

The other important aspect of Khomeini's legacy that has made a major contribution to defining Ahmadinejad's presidency has been the late ayatollah's edict committing Iran to develop nuclear weapons. The origins of Iran's military programme can be traced back to a letter Khomeini sent to the nation's military and political establishment just before he signed the ceasefire resolution ending the eight-year war with Iraq in July 1988. In it, he argued that Iran needed to develop nuclear weapons so that it would never again find itself in the humiliating position of agreeing to a disadvantageous agreement, which is how he regarded the ceasefire deal. Since then successive Iranian regimes - including that of the so-called moderate, Muhammad Khatami - have pressed ahead with acquiring the technical capability to develop an atomic bomb, irrespective of the international hostility this programme has attracted.