There are two states in the world which have nuclear weapons, the USA and Israel. Both are clear and present dangers to the entire planet. The greater threat is Israel, because Israel can destroy Western civilization and possibly make the entire planet uninhabitable. 

This is not because Israel can detonate thousands of nukes over the entire planet. Rather it is because Israel can nuke Russia. If that were to happen (perhaps as a result of an Israeli nuclear strike on Iran) then Russia would launch a nuclear attack against the United States (both the US and Russia remain on hair-trigger nuclear alert), and the US would retaliate in the same way. 

This is perhaps the main reason why the US gives Israel everything it wants and never criticises it, except in the gentlest way possible. The only way out of this situation is either the destruction of Israel's nuclear weapons capability or the destruction (or at least dismantling) of Israel itself.

The Israelis are fairly close mouthed about their nukes. Given that they are very gobby when they want to be this has to be a deliberate decision. An admission might well fall foul of American laws regarding aid. Not that Americans don't know but they can pretend that they don't. Israelis  want them to put the frighteners on Arabs in and round the Stolen Land of Palestine which they call Israel.

Acquiring nukes meant getting  the technology and the raw materials. Getting the uranium was done by Mossad [ motto: By treachery shalt thou make war ] using their standard techniques, thieving and treachery. Getting the technology was done by thieving too. There were a lot of Jews on the Manhattan Project including Oppenheimer. Most of the spies were Jews too.

The operation to get their first two hundred tons of uranium oxide was called PLUMBAT and involved conning a German businessman called Herbert Schulzen of decent background who felt a sense of guilt regarding German extermination operations. His firm was called Asmara Chemie and he used it buy the uranium in order to make soap. Was someone playing it for laughs? Perhaps but the mining outfit and the International Atomic Energy Agency swallowed it. It was to be picked up in Antwerp and shipped to Milan. 

The ship was an old rust bucket owned by Mossad through cut outs which eventually got it to Israel and Dimona. When the ship didn't arrive in Milan there was a major upset and the IAEA moved the goal posts to make sure that it didn't happen again. Has that stopped them? I doubt it. For a retelling of the story see Espionage: The Greatest Spy Operations of the Twentieth Century by Ernest Volkman.

Later Mordechai Vanunu decided to tell the world about their nuclear works at Dimona so they kidnapped him and put him in solitary for a couple of decades.

Mordechai Vanunu
Mordechai Vanunu (born 14 October 1954) is a former Israeli nuclear technician who, citing his opposition to weapons of mass destruction, revealed details of Israel's nuclear weapons program to the British press in 1986. He was subsequently lured to Italy by a female Mossad agent, where he was drugged and kidnapped by Israeli intelligence agents. He was transported to Israel and ultimately convicted in a trial that was held behind closed doors.

Vanunu spent 18 years in prison, including more than 11 in solitary confinement. Released from prison in 2004, he became subject to a broad array of restrictions on his speech and movement. Since then he has been arrested several times for violations of those restrictions, including giving various interviews to foreign journalists and attempting to leave Israel. He says he suffered "cruel and barbaric treatment" at the hands of Israeli authorities while imprisoned, and suggests that his treatment would have been different if he were Jewish (Vanunu is a Christian convert from Judaism).

Israeli authorities state that their reason of these forbiddances and liberties restrictions is fear of his spreading further state secrets and that he is still bound by his non-disclosure agreement. These stipulate that he must inform the authorities in advance about his place of residence, his movements between cities, and whom he intends to meet.

In 2007, Vanunu was sentenced to six months in prison for violating terms of his parole. The sentence was considered unusual even by the prosecution who expected a suspended sentence. In response, Amnesty International issued a press release on 2 July 2007, stating that "The organisation considers Mordechai Vanunu to be a prisoner of conscience and calls for his immediate and unconditional release." In May 2010, Vanunu was arrested and sentenced to three months in jail on suspicion that he met foreigners in violation of conditions of his 2004 release from jail.

Vanunu has been characterized internationally as a whistleblower and by Israel as a traitor. Daniel Ellsberg has referred to him as "the preeminent hero of the nuclear era". In 2010, the British artist Richard Hamilton completed a painting based on the famous press photograph of Vanunu in transit after his kidnapping, with the information concerning his capture in Rome scrawled on his hand for the press outside.