Since 2000, the ADF's expanded force structure and deployment capabilities have been put to the test on several occasions. Following the 11 September 2001 terrorist attacks on the United States, Australia committed a special forces task group and an air-to-air refuelling aircraft to operations in Afghanistan, and naval warships to the Persian Gulf as Operation Slipper. In 2003, approximately 2,000 ADF personnel, including a special forces task group, three warships and 14 &lt;a href="F/A-18%20Hornet"&gt;F/A-18 Hornet&lt;/a&gt; aircraft, took part in the invasion of Iraq.