The Bush administration then turned its attention to Iraq, and argued the need to remove Saddam Hussein from power in Iraq had become urgent. Among the stated reasons were that Saddam's regime had tried to acquire nuclear material and had not properly accounted for biological and chemical material it was known to have previously possessed, and believed to still maintain. Both the possession of these weapons of mass destruction (WMD), and the failure to account for them, would violate the U.N. sanctions. The assertion about WMD was hotly advanced by the Bush administration from the beginning, but other major powers including China, France, Germany, and Russia remained unconvinced that Iraq was a threat and refused to allow passage of a UN Security Council resolution to authorize the use of force. Iraq permitted UN weapon inspectors in November 2002, who were continuing their work to assess the WMD claim when the Bush administration decided to proceed with war without UN authorization and told the inspectors to leave the country. The United States invaded Iraq on March 20, 2003, along with a "coalition of the willing" that consisted of additional troops from the United Kingdom, and to a lesser extent, from Australia and Poland. Within about three weeks, the invasion caused the collapse of both the Iraqi government and its armed forces, however, the U.S. and allied forces failed to find any weapon of mass destruction in Iraq. Traces of former materials and weapons labs were reported to have been located, but no "smoking guns". Nevertheless, on May 1, George W. Bush landed on the aircraft carrier USS Abraham Lincoln, in a Lockheed S-3 Viking, where he gave a speech announcing the end of "major combat operations" in the Iraq War. Bush's approval rating in May was at 66%, according to a CNN–USA Today–Gallup poll. However, Bush's high approval ratings did not last. First, while the war itself was popular in the U.S., the reconstruction and attempted "democratization" of Iraq lost some support as months passed and casualty figures increased, with no decrease in violence nor progress toward stability or reconstruction. Second, as investigators combed through the country, they failed to find the predicted WMD stockpiles, which led to debate over the rationale for the war.