Barak's Tuesday tweet addressed growing worries about the growing presence of ultra-nationalist and ultra-religious factions in Israel's government. Finance minister Bezalel Smotrich and his Religious Zionism party, for example, openly aspire to turn Israel into a theocracy. 

Barak wrote: 

"In conversations between Israelis and Western diplomatic officials, there are deep concerns raised of the possibility that if the coup in Israel succeeds, a messianic dictatorship — that possesses nuclear weapons and fanatically wishes for a confrontation with Islam centered on the Temple Mount — will be established in the heart of the Middle East."  

Thanks in part to a former nuclear technician's 1986 revelations, Israel is widely known to have a nuclear arsenal, with one estimate sizing it at 90 warheads. However, it's never joined the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). It's just one of only five countries in the world that haven't done so, along with North Korea, India, Pakistan and South Sudan.