Construction began in secret in 1958 with the help of France, which helped build Israel a 24-megawatt heavy-water reactor as part of a clandestine weapons program, believed to have been completed in 1965, with their first functional nuclear device produced before June of 1967.

When U.S. officials first inquired about the site, Israeli representatives described it as a textile plant, a metallurgical research installation, and a pumping station. When American inspectors were eventually granted limited access in 1965, Israeli engineers installed temporary false walls and physically blocked entire sections of the underground complex. The inspectors reported to Washington that their visits were useless, and inspections ended in 1969.

Photographic evidence leaked by Israeli technician Mordechai Vanunu in 1986, from which experts estimated a stockpile of 100 to 200 nuclear devices, confirmed that Israel has developed thermonuclear bomb capability. After leaking this information, Vanunu was kidnapped by Mossad and sentenced to 18 years in prison.

Israel's policy of amimut, the Hebrew word for ambiguity, combines three elements: the strict secrecy about the program's existence, refraining from testing, and the managed leakage of evidence to allow Israel threat capabilities without ever making an official admission. The veiled threat repeated by successive Israeli prime ministers has been: "Israel will not be the first country to introduce nuclear weapons into the Middle East." In November 1968, the Israeli Ambassador formally informed the U.S. State Department that Israel's understanding of "introducing" weapons meant testing, deploying, or making them public, and that merely possessing weapons did not constitute "introduction."