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.
Treaty on the Non-Proliferation of Nuclear Weapons
Several NPT states parties have given up nuclear weapons or nuclear weapons programs. South Africa undertook a nuclear weapons program, but has since renounced it and acceded to the treaty in 1991 after destroying its small nuclear arsenal; after this, the remaining African countries signed the treaty. The former Soviet Republics where nuclear weapons had been based, namely Ukraine, Belarus and Kazakhstan, transferred those weapons to Russia and joined the NPT by 1994 following the signature of the Budapest Memorandum on Security Assurances.