1993 in retaliation for Hussein's attempt on former President Bush's life and again in 1996 in retaliation for Hussein's targeting of American aircraft patrolling the no-fly zones over Northern and Southern Iraq and the launching of a major offensive against the city of Irbil in Iraqi Kurdistan in violation of UNSC Resolution 688 prohibiting repression of Iraq's ethnic minorities. On September 16, 2004 Kofi Annan, the secretary general of the United Nations, said of the invasion, "I have indicated it was not in conformity with the UN charter. From our point of view, from the charter point of view, it was illegal." Furthermore, before the invasion even the then UK Attorney General, Lord Goldsmith, advised that the war would likely be illegal for several reasons including the lack of a Security Council resolution. He later changed his mind when it appeared that the invasion would take place regardless of the legal situation. Even prominent supporters of the war have accepted that it was illegal. Richard Perle, a hawkish member of the Pentagon has stated that "international law ... would have required us to leave Saddam Hussein alone." On the day Resolution 1441 was passed, the US ambassador to the UN, John Negroponte, assured the Security Council that there were no "hidden triggers" with respect to the use of force, and that in the event of a "further breach" by Iraq, resolution 1441 would require that "the matter will return to the Council for discussions as required in paragraph 12." However, he then added: "If the Security Council fails to act decisively in the event of further Iraqi violations, this resolution does not constrain any Member State from acting to defend itself against the threat posed by Iraq or to enforce relevant United Nations resolutions and protect world peace and security." Troop levels The troop level for the initial invasion of Iraq was controversial throughout the run-up to the war, particularly among U.S. military personnel. In 1999, then head of United States Central Command Marine General Anthony Zinni (ret.) organised a series of war games known as Desert Crossing to assess an invasion aimed at unseating Saddam Hussein. His plan, which predicted much of the violence and instability that followed the actual invasion, called for a force of 400,000 troops. Consistent with the Desert Crossing scenarios, the original U.S. army plan for the invasion of Iraq contemplated troop levels of up