Nuclear triad
Israel is known to have nuclear-capable aircraft and land-base missiles, with the addition of nuclear-armed submarines this would mean that they now have a full triad of land-, air-, and sea-based nuclear delivery systems some of which would be invulnerable to a first strike by an enemy for the first time in their country's history. No other nation in the Middle East in known to be in possession of nuclear weapons, even though Iran, Iraq, Syria and Libya have started development programs that were never completed.
Nuclear weapons and Israel
However, Israel maintains a policy of deliberate ambiguity, never officially denying nor admitting to having nuclear weapons, instead repeating over the years that "Israel will not be the first country to introduce nuclear weapons to the Middle East". Israel has also declined to sign the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) despite international pressure to do so, saying that would be contrary to its national security interests.