The US is sending more Patriot defense systems to the Middle East. They cost $1.1 billion each.

• The Patriot is a missile air defense system that can reach aerial targets up to 66,000 feet.
• It's a highly sought-after defense system that costs $1.1 billion each.

The US has sent more of its valuable surface-to-air missile defense systems, known as the Patriot battery, to the Middle East following attacks on American troops in Iraq and Syria in recent weeks, The Wall Street Journal reported.

Dozens of US troops in Iraq and Syria have been injured in the past month due to attacks that the Pentagon has attributed to Iran-backed militia groups.

Pentagon officials said that militant groups have carried out nearly 50 attacks since October 17 on bases housing US personnel, The Associated Press reported. These attacks have been conducted with rockets and drones, officials say.

In response to the "recent escalations by Iran and its proxy forces across the Middle East Region," Secretary of Defense Lloyd J. Austin announced on October 21 several steps to increase "force posture," including the deployment of more Patriot battalions throughout the region.

The Department of Defense did not disclose the number of Patriot batteries it was sending. Still, people familiar with the matter told the Journal that the US had sent six, doubling the number of defense systems that were already deployed.

It's not known precisely where these systems will be deployed.

According to the Missile Defense Advocacy Alliance, a nonprofit that promotes ballistic missile defense development, Israel currently operates three Patriot batteries. These systems were critical to the country's air defense during the 2014 Gaza War, taking down armed unmanned aerial vehicles and other aircraft.

A DOD spokesperson declined to provide further comment.

The missile defense systems are produced by Raytheon, a contractee of the US government, and cost about $1.1 billion each.

Some of the significant components of the system include a launching system for the missiles, a radar that detects targets, a control station, and a generator, according to a Congressional Research Service (CRS) report.

Though official ranges are unknown, the CRS report stated that the "flight ceiling" for one of the interceptors is about 20 km or about 66,000 feet.

Eighteen countries currently operate Patriot, according to the Center for Strategic & International Studies, including Ukraine, which received the first one from the US in April.

US officials have said that the defense system has been used to shoot down a Russian hypersonic missile and to defend itself from attacks.