On June 7, 1981, an Israeli Air Force strike force left Etzion air base and flew 1,100 km (683.5 mi) across Jordan, Saudi Arabia and into Iraq to bomb the Osariq Nuclear Reactor. Arriving at around 17:30, the strike force quickly destroyed the reactor site. The strike force evaded detection by flying so close to each other on the long journey that, instead of appearing as a squadron of small fighters on radar, they appeared as a single large jet, and not much attention was given to them. One of the Israeli pilots on the mission was Ilan Ramon, who would later become Israel's first astronaut and die in the Space Shuttle Columbia disaster on February 1, 2003.
Osiraq was a 40 MW light water nuclear materials testing reactor (MTR) in Iraq. It was constructed by the Iraqi government at the Al Tuwaitha Nuclear Research Centre, 18 km south-east of Baghdad in 1977.
The Israeli government was deeply concerned at this purchase. Despite Iraqi claims that the plant was for peaceful use, it was an unusual choice — an MTR design is useful for countries with established nuclear reactor construction programs, but less so otherwise. The reactor used HEU fuel as standard. The substantial Iraqi purchases of uranium ore could be treated at the plant to produce plutonium, and the Iraq government had also purchased a fuel fabrication plant and a recovery 'hot cell'. Further, Iraq being one of the world's leading oil and natural gas suppliers made the notion of them needing a peaceful nuclear energy plant even more unlikely.
However, the plant was under IAEA supervision and was regularly inspected, and there were also French technicians in constant attendance. The supply of HEU as fuel was carefully staggered, and used fuel had to be returned to France, making a diversion of fuel into a weapons program obvious and therefore unlikely; any noticed diversion would have meant an immediate end to further supplies. Similarly, the clandestine irradiation of uranium could not have taken place undetected; the repeated, slow, and costly changing of uranium rods would have been obvious.
Although most agreed that Iraq was years away from being able to build a nuclear weapon, the Iranians and the Israelis felt any raid must occur well before nuclear fuel was loaded to prevent nuclear fallout. Further, Israel's Menachem Begin, feared that Israel's next elected government would not act until a nuclear weapon was created.
The Iranian attack on the site on September 30, 1980 had little success. After Israeli intelligence agencies confirmed to Menachem Begin Iraq's intent to use the reactor to produce weapons, Begin then authorized an Israeli strike to take place. The attack was regarded as being in breach with the United Nations Charter and international law and was widely condemned. The Security Council passed a unanimous resolution where it "strongly condemns the military attack by Israel in clear violation of the Charter of the United Nations and the norms of international conduct." (S/RES/487).
(taken from the Wikipedia entry on Osiraq)