Israel's survival will depend on having a credible and reliable nuclear deterrent. Although it is possible for Israel to avoid a nuclear threat, Israel must remain alert for first-strike aggression. In such cases, Israel could first use conventional weapons and then resort nuclear counter-retaliation to defeat the enemy.
This is a very real dilemma for Israel. A strategic calculation of the benefits and costs of a strike would need to be made. Jerusalem's assessment on the enemy and its essential damage-limitation would help to calculate this calculation. If the enemy's intentions are clear, then a nuclear first strike might be justified. The first strike might not be the right decision if Jerusalem is unsure.
With the right strategic circumstances, it is possible to strike first preemptively in spite of the dangers. A defensive first strike is legal, as long as it is justified under international law. A strike by the enemy to disrupt Israel's military order of battle would be illegal. An enemy might launch a preemptive strike or a chemical or biological attack to impede the strike.
If Israel opts to preemptively target Iran, then the enemy's reaction would dictate Israel’s next steps. The preemption process will influence the enemy's reaction by its strategic and jurisprudential assessment. Depending on the severity and extent of the provocations, the enemy's reaction would be judged rational or irrational. If the enemy's response to the provocations is unreasonable, the enemy can choose to strike first and thus immobilize Israel's battle order.
Israel might then be tempted by Iran to strike first with conventional weapons, before resorting to nuclear retaliation. In such cases, the decision makers would consider whether Iran's arsenal of nuclear weapons could deter Israel, and whether Iran's counterretaliation would prevent Israel from attacking. If the enemy responds only to conventional retaliation the nuclear counter-retaliation is not possible.
Israel must ensure that its strategies and tactics are legal and that it follows authoritative expectations, before it preemptively attacks Iran. It would also be prudent to take into account Iran's reciprocal judgments. It is possible that Israel will preemptively strike Iran and then retaliate using conventional weapons against Iran. This could create a false pretext to aggression.
The strategic decisions of Jerusalem would also be affected by the nature of Israel's nuclear strategy and nuclear arsenal. Israel could be less likely, if it had nuclear weapons to, to threaten nukes for territorial infringements. Israel may not have nuclear weapons and could therefore be less likely to threaten nukes for terrorist incursions.
Jerusalem would also be able to use nuclear weapons, and would likely have a nuclear arsenal, if the enemy had a nuclear weapon arsenal. Israeli decision-makers determine if Iran’s nuclear arsenal could deter Israel. If Iran’s nuclear weapons could deter Israel's attack, then the Israeli decision to strike preemptively would be legal. If Iran's atomic arsenal did not deter Israel from attacking, then the decision would be illegal.