The Patriot is a surface-to-air missile system used to shoot down aircraft, cruise missiles and ballistic missiles.

A Patriot battery has four main parts. A radar finds and tracks targets. A control station plans the intercept. Launchers hold the missiles. A power unit keeps everything running.

The radar scans the sky and locks onto a threat. The control station calculates where the missile and the threat will meet. A Patriot interceptor then launches and destroys the target in mid-air.

Newer PAC-3 interceptors hit the target directly instead of exploding nearby. This hit-to-kill design works better against fast ballistic missiles.

One battery can guard a wide area, but not a whole country. Governments often move batteries to protect key sites such as airports, oil plants and military bases.

The system is in demand. Recent wars have shown how quickly interceptors are used up. Experts say producing enough missiles is now a major challenge.