By Michael Martinez and Josh Levs
Editor's note: A version of this report originally was published in November 2012.
(CNN) -- Israel is fighting to block rockets from striking its major population centers, deploying its Iron Dome missile defense system to intercept them.
By Wednesday afternoon, since the start of Operation Protective Edge, the Israel Defense Forces said missiles from the system had intercepted 56 rockets fired out of Gaza, preventing strikes in Jerusalem, Tel Aviv, Ashdod, Ashkelon, Kiryat Gat and elsewhere.
More than 250 rockets have been fired out of Gaza toward Israel in that time, the IDF said. Israel uses the Iron Dome system only against rockets headed toward populated areas. If one appears to be headed for an empty field, the dome does not activate.
The system is a centerpiece of Israel's defense strategy.
How does it work?
The name Iron Dome evokes an image of a protective bubble over a city. In practice, it targets incoming rockets and fires an interceptor missile to destroy them in the air.
Each battery has a firing-control radar to identify targets. It also has a portable missile launcher. The system is easily transportable, with just a few hours needed to relocate and set up.
The missile is highly maneuverable. It is 3 meters, or almost 10 feet, long; has a diameter of about 6 inches (15 centimeters); and weighs 90 kilograms, or 198 pounds, the security analysis group IHS Jane's said in 2012.
The warhead is believed to carry 11 kilograms, or 24 pounds, of high explosives, IHS Jane's said. Its range is from 4 kilometers to 70 kilometers, or 2½ miles to 43 miles.
Iron Dome confronts multiple threats simultaneously, in all weather conditions, the military said. Israel credits "breakthrough technology" and the system's radar.
"The radar detects a rocket launch and passes information regarding its path to the control center, which calculates the predicted point of impact," the IDF said. "If this location justifies an interception, a missile is fired to intercept the rocket. The payload of the interceptor missile explodes near the rocket, in a place that is not expected to cause injuries."
What are the origins?
Israel began developing the ground-based system in 2007.
After a series of test flights in 2008 and 2009, the first deployment of a battery occurred in southern Israel in 2011. The Israel Air Force reported an interception success rate of 70% in 2011, IHS Jane's said.
Is the United States involved in Iron Dome?
The initial development was solely by Israel's defense technology company Rafael, but the system has since been heavily sponsored by the United States.
In 2014, the United States provided $235 million for Iron Dome research, development and production, according to the Congressional Research Service.
"This is a program that has been critical in terms of providing security and safety for Israeli families," President Obama has said of Iron Dome. "It is a program that has been tested and has prevented missile strikes inside of Israel."
Each Iron Dome battery costs $50 million, IHS Jane's said. A missile costs at least $62,000, Israeli officials said.
Other countries have expressed interest in buying the system, including the United States, South Korea and several NATO countries in Europe with military forces in Afghanistan, The Jerusalem Post has reported.
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