On Tuesday, Israel amped up its military offensive in the Gaza Strip in response to the more than 200 rockets fired upon them over the last month from Hamas. The response, called Operation Protective Edge, involves air strikes as well as the country's primary missile defense system, the "Iron Dome," which was built to protect Israel from short-range, unguided rockets on ballistic trajectories.

By Wednesday afternoon the Iron Dome had intercepted 56 rockets and prevented strikes on Jerusalem, Tel Aviv, Ashdod, Ashkelon and Kiryat Gat.

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Iron Dome is not an actual dome, but a small, mobile arsenal that consists of a radar unit and typically three launchers capable of deploying missile interceptors and missiles. It was up in running for the first time on March 27, 2011 and currently there are five batteries of Iron Dome missile interceptors deployed.

It works when radar picks up the signal of an incoming rocket -- most of which are unguided -- within an approximately 40-mile radius.

The information is sent to a control center on a truck and operators check the trajectory of the rocket. If it's headed to a populated area or a military target, an Iron Dome missile, called a Tamir, is fired. This missile is guided and therefore more accurate than the attacking missile. A solider programs the Tamir with the incoming rocket's trajectory and then guides it with the help of radar. When the Tamir reaches the rocket, it detonates, destroying it.

Iron Dome was developed by three Israeli companies: Rafael Advanced Defense Systems, who built the Tamir missile; Elta, who designed the radar; and Impress, who developed the command and control systems.

This promotional video shows how the system works.

The construction of the Iron Dome was financed largely with aid from the United States, amounting to $310 million so far and another $610 million over the next three years, according to The New York Times.

One issue with the system is the high price tag. Each Tamir cost up to $50,000, while the typical Qassam rocket launched form Gaza is less than $1,000. That means that Palestinians can launch a lot more rockets at much less expense. Even if Israel were to deploy many more batteries, it's possible the Palestinians could fire enough rockets to simply overwhelm the interceptors.

The latest surge in violence in the region was ignited by the recent kidnapping and killing of three Israeli youths as well as a Palestinian teen. As of Thursday morning, at least 74 Palestinian civilians have been killed as part of Israel's Gaza offensive.

Editor's note: A version of this article originally ran Nov. 19, 2012.