Iran's recent attempt to ship arms to Hamas in Gaza is an act of war committed by the Iranian government against the Israeli government. The Israeli Navy seized the ship, loaded with weapons designed to kill Israeli civilians, and traced the weapons back to Iran. Nor is this the first act of war that would justify a military response by Israel under international law. Iran has sent other boatloads of anti personnel weapons to Hamas and Hezbollah. In addition, back in 1992, the Iranian leaders planned and authorized a deadly attack on Israel's embassy in Argentina. That bombing, which was carried out by Iranian agents, constituted a direct armed attack on the state of Israel, since its embassy is part of its sovereign territory. Moreover, the Iranian government has publicly declared war on Israel by calling for it "to be wiped off the map."

Under international law, these acts of war -- known as Casus Belli -- fully justify an Israeli armed response. Even the UN Charter authorizes a unilateral response to an armed attack. Providing weapons to a declared enemy in the face of an embargo has historically been deemed an armed attack under the law of war, especially when those providing the weapons intend for them to be used against the enemy's civilians. So too is the bombing of an embassy.

Two other recent events enhance Israel's right use military means to prevent Iran from continuing to arm Israel's enemies. The recent disaster in Japan has shown the world the extraordinary dangers posed by nuclear radiation. If anybody ever doubted the power of a dirty bomb to devastate a nation, both physically and psychologically, those doubts have been eliminated by what is now going on in Japan. If Iran were to develop nuclear weapons, the next ship destined to Gaza might contain a nuclear dirty bomb and Israel might not intercept that one. A dirty bomb detonated in tiny Israel would cause incalculable damage to civilian life.

Moreover, the recent killings in Itamar of a family including three children, demonstrate how weapons are used by Israel's enemies against civilians in violation of the laws of war. Even babies are targeted by those armed by Iran. Hamas praised the murders.

Israel has the right to prevent its civilians from being murdered by Iranian weapons, especially weapons of mass destruction. Iran would have no legal standing to protest a surgical attack on its nuclear facilities that are designing weapons that could be used to achieve Iran's declared goal of wiping Israel off the map and killing millions of its citizens. The leaders of Iran have publicly declared that a nuclear exchange, killing millions of Jews and Muslims, would be acceptable to them because it would destroy Israel while only damaging Islam. A suicide nation cannot be deterred by the threat of retaliation. Israel's only realistic option may be a preventive military strike of the kind it conducted against Iraq's nuclear reactor in 1981. That surgical attack may have saved countless lives at the cost of one single casualty. By the way, Iran too tried to destroy Iraq's nuclear reactor, but failed. Certainly Israel has the right to do what Iran itself tried to do -- namely prevent a lethal enemy from developing weapons capable of mass murder of its citizens.

This is not to say that Israel should attack Iran's nuclear reactors now. That it has the right to do so does not mean that it should not wait for a more opportune time. The law of war does not require an immediate military response to an armed attack. The nation attacked can postpone its counterattack without waiving its right. The military option should always be a last resort after all other efforts have failed. It may well be that efforts to permanently disable Iran's nuclear computers will succeed. Although it is unlikely that economic sanctions will ever persuade Iran's ideological zealots to end their nuclear weapons program, a combination of quasi military, tough economic and diplomatic sanctions may slow it down to a point where the military option can be postponed. But under no circumstances should the military option ever be taken off the table. Israel must preserve its ability to exercise its fundamental right of preventive self defense. If possible, it should act together with other allies. But if necessary, it has the right to act alone to protect its citizens. Nearly everybody hopes that it won't come to that, but hope is not a policy. As George Washington cautioned in his second inaugural address, "To be prepared for war is one of the most effectual means of preserving peace."