The United States is sending four Patriot batteries, armed with the PAC-3 anti-missile missiles, to Okinawa. These batteries will defend U.S. bases there against North Korean attack. PAC-3 missiles cost $3.2 million each and are the result of two decades of development.First used during the 1991 Gulf War, the current (PAC-3) version shot down two Iraqi missiles in 2003. During the 2003 operation, 22 Patriot missiles were fired. Two of these took down two coalition aircraft. Electronic and software problems caused the IFF (Identify Friend or Foe) systems to fail.
This is less of a problem with incoming missiles, as they are rarely friendly. Chinese war plans are believed to include ballistic missile attacks as well, and one of the targets is said to be Okinawa.