The Iran-Iraq was itself a particularly complicated conflict, sparked by a combination of historical border disputes between the two nations and Saddam Hussein's fear that the new Iranian government would incite Iraqi Shias to overthrow the Ba'athist Party (as an aside: Hussein's fears were perhaps prophetic both with respect to Iran's involvement in Iraq after the 2003 invasion by the United States, as well as its intervention and support of the Shi'ite group Hezbollah and its support of Alawite Bashar al-Assad in Syria). Whatever its causes, Iraq invaded Iran in September of 1980. Eight days into the war, Iranian fighter planes flew low over Iraq and headed toward Tuwaitha and the Osirak reactor. Iranian planes struck the reactor and damaged it, but failed to destroy the reactor completely. Saddam Hussein's scientists and his team, along with French scientists, began work to repair the reactor and eventually did so. When it happened, Iran's attack on the Osirak power plant was the first ever military strike on a nuclear facility. In a great bit of foreshadowing, Hussein was so shocked by the attack on the reactor due to his gross underestimation of Iranian air power that he assumed that Israel was behind the strike.
Nine months later, on June 7, 1981, Israeli fighters struck and destroyed the Osirak reactor, flying through Saudi and Iraqi airspace before bombing the reactor. The world was in an uproar, decrying the preemptive Israeli airstrike on a nuclear reactor that had been struck by Iranian warplanes less than a year earlier. The leadup to the attack certainly proved the old maxim that "the enemy of my enemy is my friend" when Revolutionary Iran and Israel worked together to derail the Iraqi nuclear program through an Israeli strike. While there is dispute over the exact nature of the collaboration, many sources agree that Iran provided intelligence, photographs of the region and possibly offered to let Israeli pilots emergency land at Tabriz. Documents found in Hussein's personal effects and released in October of 2011 lent credibility to the idea that the Osirak reactor was to be used for military purposes, as Hussein was recorded as saying "Once Iraq walks out victorious (in the Iran-Iraq War), there will not be any Israel,” Hussein. “Technically, they (the Israelis) are right in all of their attempts to harm Iraq.”
While Israel was criticized for its 1981 strike on Osirak, the fact was that neither Israel nor Iran put much stock in Iraqi and French claims Saddam Hussein would not use the nuclear facility being constructed by the French outside Baghdad to create nuclear weapons to use on Iran. Indeed, Saddam's subsequent use of chemical weapons during the conflict showed his willingness to use weapons of mass destruction against Iranian soldiers. Obviously, the circumstances of bombing the nuclear reactor in the larger context of open warfare presents a different scenario than Israel currently faces with respect to Iran's nuclear program. However, Iran's anti-Israel language calling for Israel to be wiped off the face the earth harkens back to Saddam Hussein's assertions about Iran's attempts to conquer the Arab states and extend Shi'ite influence over the Sunni. Hussein himself believed that the Arabs' two great enemies were the Persians and the Israelis. Iran's government holds views of the "Zionists" that are substantially identical to those held by Hussein, beliefs that led to him launching SCUDs at Israel during the Gulf War.
Given all this history, it is understandably difficult for the Israelis to rest easy when being told that Iran has no nuclear intentions. After all, if such assurances from the West (notably France) weren't good enough for the Iranians in 1980, why should they be good enough for the Israelis in 2013?