Israel declared the completion of a sensor-equipped subterranean wall on its side of the Gaza border on Tuesday, a counter-measure devised after Hamas terrorists exploited tunnels to surprise Israeli soldiers in a 2014 assault.

In 2016, Israel made the project, which includes an above-ground fence, a naval barrier, radar equipment, and command and control buildings, public.

According to a defense ministry statement, “the barrier, which is an innovative and highly complex initiative, deprives Hamas of one of the capabilities it wanted to build.”

“It (the project) places a ‘iron wall,’ sensors, and concrete between the terror group and the citizens of Israel’s south,” he said of the project, which beefs up an existing border barrier.

According to the ministry, the barrier, which contains hundreds of cameras, radars, and other sensors, covers 65 kilometers (40 miles) and required 140,000 tonnes of iron and steel to build over 3.5 years.

The project’s “smart fence” is more than 6 meters (20 feet) tall, and its marine barrier includes measures to detect invasion by sea as well as a remote-controlled weapons system, according to the company. The depth of the subsurface wall was not disclosed by the government.

Gaza also has a 14-kilometre-(8.7-mile)-long border with Egypt, which has also clamped down on crossings, citing security concerns. Since 2013, Egyptian forces have demolished smuggling tunnels while Hamas, on its side, has stepped up patrols.

Israel and Hamas have fought four wars since the Islamist group seized control the coastal Gaza Strip in 2007 from forces loyal to Palestinian President Mahmoud Abbas.

In the latest conflict, last May, Hamas and other militant groups fired more than 4,300 rockets at Israel, which deployed Iron Dome interceptors against them and carried out extensive air strikes in Gaza.