During the 1973 Yom Kippur War when Israel’s back was against the wall, and things looked dire, Israel armed some of its land-based missiles with nukes and some of its warplanes with nukes and ordered a nuclear alert. Their targets: Syria’s and Egypt’s capitals and command and control sites. If the tide of the war had not turned, the consensus among intelligence experts is that Israel would have issued the GO and LAUNCH orders.
The difference now, is that Israel has 5 submarines equipped with nuclear cruise missiles. Highly mobile and hard to detect. Their newest sub INS_Drakon is being equipped with vertically launched nuclear missiles capable of reaching all of Iran.